NAME¶
fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server
SYNOPSIS¶
fetchmail [
option...] [
mailserver...]
fetchmailconf
DESCRIPTION¶
fetchmail is a mail-retrieval and forwarding utility; it fetches mail
from remote mailservers and forwards it to your local (client) machine's
delivery system. You can then handle the retrieved mail using normal mail user
agents such as
mutt(1),
elm(1) or
Mail(1). The
fetchmail utility can be run in a daemon mode to repeatedly poll one or
more systems at a specified interval.
The
fetchmail program can gather mail from servers supporting any of the
common mail-retrieval protocols: POP2 (legacy, to be removed from future
release), POP3, IMAP2bis, IMAP4, and IMAP4rev1. It can also use the ESMTP ETRN
extension and ODMR. (The RFCs describing all these protocols are listed at the
end of this manual page.)
While
fetchmail is primarily intended to be used over on-demand TCP/IP
links (such as SLIP or PPP connections), it may also be useful as a message
transfer agent for sites which refuse for security reasons to permit
(sender-initiated) SMTP transactions with sendmail.
SUPPORT, TROUBLESHOOTING¶
For troubleshooting, tracing and debugging, you need to increase fetchmail's
verbosity to actually see what happens. To do that, please run
both of the
two following commands, adding all of the options you'd normally
use.
-
env LC_ALL=C fetchmail -V -v --nodetach --nosyslog
- (This command line prints in English how fetchmail understands your
configuration.)
-
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog
- (This command line actually runs fetchmail with verbose English
output.)
Also see
You can omit the LC_ALL=C part above if you want output in the local language
(if supported). However if you are posting to mailing lists, please leave it
in. The maintainers do not necessarily understand your language, please use
English.
CONCEPTS¶
If
fetchmail is used with a POP or an IMAP server (but not with ETRN or
ODMR), it has two fundamental modes of operation for each user account from
which it retrieves mail:
singledrop- and
multidrop-mode.
- In singledrop-mode,
- fetchmail assumes that all messages in the user's account (mailbox)
are intended for a single recipient. The identity of the recipient will
either default to the local user currently executing fetchmail, or
will need to be explicitly specified in the configuration file.
- fetchmail uses singledrop-mode when the fetchmailrc configuration
contains at most a single local user specification for a given server
account.
- In multidrop-mode,
- fetchmail assumes that the mail server account actually contains
mail intended for any number of different recipients. Therefore,
fetchmail must attempt to deduce the proper "envelope
recipient" from the mail headers of each message. In this mode of
operation, fetchmail almost resembles a mail transfer agent
(MTA).
- Note that neither the POP nor IMAP protocols were intended for use in this
fashion, and hence envelope information is often not directly available.
The ISP must stores the envelope information in some message header
and. The ISP must also store one copy of the message per recipient.
If either of the conditions is not fulfilled, this process is unreliable,
because fetchmail must then resort to guessing the true envelope
recipient(s) of a message. This usually fails for mailing list messages
and Bcc:d mail, or mail for multiple recipients in your domain.
- fetchmail uses multidrop-mode when more than one local user and/or
a wildcard is specified for a particular server account in the
configuration file.
- In ETRN and ODMR modes,
- these considerations do not apply, as these protocols are based on SMTP,
which provides explicit envelope recipient information. These protocols
always support multiple recipients.
As each message is retrieved,
fetchmail normally delivers it via SMTP to
port 25 on the machine it is running on (localhost), just as though it were
being passed in over a normal TCP/IP link.
fetchmail provides the SMTP
server with an envelope recipient derived in the manner described previously.
The mail will then be delivered according to your MTA's rules (the Mail
Transfer Agent is usually
sendmail(8),
exim(8), or
postfix(8)). Invoking your system's MDA (Mail Delivery Agent) is the
duty of your MTA. All the delivery-control mechanisms (such as
.forward
files) normally available through your system MTA and local delivery agents
will therefore be applied as usual.
If your fetchmail configuration sets a local MDA (see the --mda option), it will
be used directly instead of talking SMTP to port 25.
If the program
fetchmailconf is available, it will assist you in setting
up and editing a fetchmailrc configuration. It runs under the X window system
and requires that the language Python and the Tk toolkit (with Python
bindings) be present on your system. If you are first setting up fetchmail for
single-user mode, it is recommended that you use Novice mode. Expert mode
provides complete control of fetchmail configuration, including the multidrop
features. In either case, the 'Autoprobe' button will tell you the most
capable protocol a given mailserver supports, and warn you of potential
problems with that server.
GENERAL OPERATION¶
The behavior of
fetchmail is controlled by command-line options and a run
control file,
~/.fetchmailrc, the syntax of which we describe in a
later section (this file is what the
fetchmailconf program edits).
Command-line options override
~/.fetchmailrc declarations.
Each server name that you specify following the options on the command line will
be queried. If you don't specify any servers on the command line, each 'poll'
entry in your
~/.fetchmailrc file will be queried.
To facilitate the use of
fetchmail in scripts and pipelines, it returns
an appropriate exit code upon termination -- see EXIT CODES below.
The following options modify the behavior of
fetchmail. It is seldom
necessary to specify any of these once you have a working
.fetchmailrc
file set up.
Almost all options have a corresponding keyword which can be used to declare
them in a
.fetchmailrc file.
Some special options are not covered here, but are documented instead in
sections on AUTHENTICATION and DAEMON MODE which follow.
General Options¶
- -V | --version
- Displays the version information for your copy of fetchmail. No
mail fetch is performed. Instead, for each server specified, all the
option information that would be computed if fetchmail were
connecting to that server is displayed. Any non-printables in passwords or
other string names are shown as backslashed C-like escape sequences. This
option is useful for verifying that your options are set the way you want
them.
- -c | --check
- Return a status code to indicate whether there is mail waiting, without
actually fetching or deleting mail (see EXIT CODES below). This option
turns off daemon mode (in which it would be useless). It doesn't play well
with queries to multiple sites, and doesn't work with ETRN or ODMR. It
will return a false positive if you leave read but undeleted mail in your
server mailbox and your fetch protocol can't tell kept messages from new
ones. This means it will work with IMAP, not work with POP2, and may
occasionally flake out under POP3.
- -s | --silent
- Silent mode. Suppresses all progress/status messages that are normally
echoed to standard output during a fetch (but does not suppress actual
error messages). The --verbose option overrides this.
- -v | --verbose
- Verbose mode. All control messages passed between fetchmail and the
mailserver are echoed to stdout. Overrides --silent. Doubling this option
(-v -v) causes extra diagnostic information to be printed.
- --nosoftbounce
- (since v6.3.10, Keyword: set no softbounce, since v6.3.10)
Hard bounce mode. All permanent delivery errors cause messages to be deleted
from the upstream server, see "no softbounce" below.
- --softbounce
- (since v6.3.10, Keyword: set softbounce, since v6.3.10)
Soft bounce mode. All permanent delivery errors cause messages to be left on
the upstream server if the protocol supports that. This option is on by
default to match historic fetchmail documentation, and will be changed
to hard bounce mode in the next fetchmail release.
Disposal Options¶
- -a | --all | (since v6.3.3) --fetchall
- (Keyword: fetchall, since v3.0)
Retrieve both old (seen) and new messages from the mailserver. The default
is to fetch only messages the server has not marked seen. Under POP3, this
option also forces the use of RETR rather than TOP. Note that POP2
retrieval behaves as though --all is always on (see RETRIEVAL FAILURE
MODES below) and this option does not work with ETRN or ODMR. While the -a
and --all command-line and fetchall rcfile options have been supported for
a long time, the --fetchall command-line option was added in v6.3.3.
- -k | --keep
- (Keyword: keep)
Keep retrieved messages on the remote mailserver. Normally, messages are
deleted from the folder on the mailserver after they have been retrieved.
Specifying the keep option causes retrieved messages to remain in
your folder on the mailserver. This option does not work with ETRN or
ODMR. If used with POP3, it is recommended to also specify the --uidl
option or uidl keyword.
- -K | --nokeep
- (Keyword: nokeep)
Delete retrieved messages from the remote mailserver. This option forces
retrieved mail to be deleted. It may be useful if you have specified a
default of keep in your .fetchmailrc. This option is forced
on with ETRN and ODMR.
- -F | --flush
- (Keyword: flush)
POP3/IMAP only. This is a dangerous option and can cause mail loss when used
improperly. It deletes old (seen) messages from the mailserver before
retrieving new messages. Warning: This can cause mail loss if you
check your mail with other clients than fetchmail, and cause fetchmail to
delete a message it had never fetched before. It can also cause mail loss
if the mail server marks the message seen after retrieval (IMAP2 servers).
You should probably not use this option in your configuration file. If you
use it with POP3, you must use the 'uidl' option. What you probably want
is the default setting: if you don't specify '-k', then fetchmail will
automatically delete messages after successful delivery.
- --limitflush
- POP3/IMAP only, since version 6.3.0. Delete oversized messages from the
mailserver before retrieving new messages. The size limit should be
separately specified with the --limit option. This option does not work
with ETRN or ODMR.
Protocol and Query Options¶
- -p <proto> | --proto <proto> | --protocol
<proto>
- (Keyword: proto[col])
Specify the protocol to use when communicating with the remote mailserver.
If no protocol is specified, the default is AUTO. proto may be one
of the following:
- AUTO
- Tries IMAP, POP3, and POP2 (skipping any of these for which support has
not been compiled in).
- POP2
- Post Office Protocol 2 (legacy, to be removed from future release)
- POP3
- Post Office Protocol 3
- APOP
- Use POP3 with old-fashioned MD5-challenge authentication. Considered not
resistant to man-in-the-middle attacks.
- RPOP
- Use POP3 with RPOP authentication.
- KPOP
- Use POP3 with Kerberos V4 authentication on port 1109.
- SDPS
- Use POP3 with Demon Internet's SDPS extensions.
- IMAP
- IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically detects
their capabilities).
- ETRN
- Use the ESMTP ETRN option.
- ODMR
- Use the the On-Demand Mail Relay ESMTP profile.
All these alternatives work in basically the same way (communicating with
standard server daemons to fetch mail already delivered to a mailbox on the
server) except ETRN and ODMR. The ETRN mode allows you to ask a compliant
ESMTP server (such as BSD sendmail at release 8.8.0 or higher) to immediately
open a sender-SMTP connection to your client machine and begin forwarding any
items addressed to your client machine in the server's queue of undelivered
mail. The ODMR mode requires an ODMR-capable server and works similarly to
ETRN, except that it does not require the client machine to have a static DNS.
- -U | --uidl
- (Keyword: uidl)
Force UIDL use (effective only with POP3). Force client-side tracking of
'newness' of messages (UIDL stands for "unique ID listing" and
is described in RFC1939). Use with 'keep' to use a mailbox as a baby news
drop for a group of users. The fact that seen messages are skipped is
logged, unless error logging is done through syslog while running in
daemon mode. Note that fetchmail may automatically enable this option
depending on upstream server capabilities. Note also that this option may
be removed and forced enabled in a future fetchmail version. See also:
--idfile.
- --idle (since 6.3.3)
- (Keyword: idle, since before 6.0.0)
Enable IDLE use (effective only with IMAP). Note that this works with only
one folder at a given time. While the idle rcfile keyword had been
supported for a long time, the --idle command-line option was added in
version 6.3.3. IDLE use means that fetchmail tells the IMAP server to send
notice of new messages, so they can be retrieved sooner than would be
possible with regular polls.
- -P <portnumber> | --service <servicename>
- (Keyword: service) Since version 6.3.0.
The service option permits you to specify a service name to connect to. You
can specify a decimal port number here, if your services database lacks
the required service-port assignments. See the FAQ item R12 and the --ssl
documentation for details. This replaces the older --port option.
- --port <portnumber>
- (Keyword: port)
Obsolete version of --service that does not take service names. Note:
this option may be removed from a future version.
- --principal <principal>
- (Keyword: principal)
The principal option permits you to specify a service principal for mutual
authentication. This is applicable to POP3 or IMAP with Kerberos 4
authentication only. It does not apply to Kerberos 5 or GSSAPI. This
option may be removed in a future fetchmail version.
- -t <seconds> | --timeout <seconds>
- (Keyword: timeout)
The timeout option allows you to set a server-nonresponse timeout in
seconds. If a mailserver does not send a greeting message or respond to
commands for the given number of seconds, fetchmail will drop the
connection to it. Without such a timeout fetchmail might hang until
the TCP connection times out, trying to fetch mail from a down host, which
may be very long. This would be particularly annoying for a
fetchmail running in the background. There is a default timeout
which fetchmail -V will report. If a given connection receives too
many timeouts in succession, fetchmail will consider it wedged and stop
retrying. The calling user will be notified by email if this happens.
- Beginning with fetchmail 6.3.10, the SMTP client uses the recommended
minimum timeouts from RFC-5321 while waiting for the SMTP/LMTP server it
is talking to. You can raise the timeouts even more, but you cannot
shorten them. This is to avoid a painful situation where fetchmail has
been configured with a short timeout (a minute or less), ships a long
message (many MBytes) to the local MTA, which then takes longer than
timeout to respond "OK", which it eventually will; that would
mean the mail gets delivered properly, but fetchmail cannot notice it and
will thus refetch this big message over and over again.
- --plugin <command>
- (Keyword: plugin)
The plugin option allows you to use an external program to establish the TCP
connection. This is useful if you want to use ssh, or need some special
firewalling setup. The program will be looked up in $PATH and can
optionally be passed the hostname and port as arguments using
"%h" and "%p" respectively (note that the
interpolation logic is rather primitive, and these tokens must be bounded
by whitespace or beginning of string or end of string). Fetchmail will
write to the plugin's stdin and read from the plugin's stdout.
- --plugout <command>
- (Keyword: plugout)
Identical to the plugin option above, but this one is used for the SMTP
connections.
- -r <name> | --folder <name>
- (Keyword: folder[s])
Causes a specified non-default mail folder on the mailserver (or
comma-separated list of folders) to be retrieved. The syntax of the folder
name is server-dependent. This option is not available under POP3, ETRN,
or ODMR.
- --tracepolls
- (Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'polling account %s'
and 'folder %s' to the Received line it generates, where the %s parts are
replaced by the user's remote name, the poll label, and the folder
(mailbox) where available (the Received header also normally includes the
server's true name). This can be used to facilitate mail filtering based
on the account it is being received from. The folder information is
written only since version 6.3.4.
- --ssl
- (Keyword: ssl)
Causes the connection to the mail server to be encrypted via SSL. Connect to
the server using the specified base protocol over a connection secured by
SSL. This option defeats opportunistic starttls negotiation. It is highly
recommended to use --sslproto 'SSL3' --sslcertck to validate the
certificates presented by the server and defeat the obsolete SSLv2
negotiation. More information is available in the README.SSL file
that ships with fetchmail.
- Note that fetchmail may still try to negotiate SSL through starttls even
if this option is omitted. You can use the --sslproto option to defeat
this behavior or tell fetchmail to negotiate a particular SSL
protocol.
- If no port is specified, the connection is attempted to the well known
port of the SSL version of the base protocol. This is generally a
different port than the port used by the base protocol. For IMAP, this is
port 143 for the clear protocol and port 993 for the SSL secured protocol,
for POP3, it is port 110 for the clear text and port 995 for the encrypted
variant.
- If your system lacks the corresponding entries from /etc/services, see the
--service option and specify the numeric port number as given in the
previous paragraph (unless your ISP had directed you to different ports,
which is uncommon however).
- --sslcert <name>
- (Keyword: sslcert)
For certificate-based client authentication. Some SSL encrypted servers
require client side keys and certificates for authentication. In most
cases, this is optional. This specifies the location of the public key
certificate to be presented to the server at the time the SSL session is
established. It is not required (but may be provided) if the server does
not require it. It may be the same file as the private key (combined key
and certificate file) but this is not recommended. Also see --sslkey
below.
NOTE: If you use client authentication, the user name is fetched
from the certificate's CommonName and overrides the name set with
--user.
- --sslkey <name>
- (Keyword: sslkey)
Specifies the file name of the client side private SSL key. Some SSL
encrypted servers require client side keys and certificates for
authentication. In most cases, this is optional. This specifies the
location of the private key used to sign transactions with the server at
the time the SSL session is established. It is not required (but may be
provided) if the server does not require it. It may be the same file as
the public key (combined key and certificate file) but this is not
recommended.
- If a password is required to unlock the key, it will be prompted for at
the time just prior to establishing the session to the server. This can
cause some complications in daemon mode.
- Also see --sslcert above.
- --sslproto <name>
- (Keyword: sslproto)
Forces an SSL/TLS protocol. Possible values are '', ' SSL2'
(not supported on all systems), ' SSL23', (use of these two values
is discouraged and should only be used as a last resort) ' SSL3',
and ' TLS1'. The default behaviour if this option is unset is: for
connections without --ssl, use ' TLS1' so that fetchmail will
opportunistically try STARTTLS negotiation with TLS1. You can configure
this option explicitly if the default handshake (TLS1 if --ssl is not
used) does not work for your server.
- Use this option with 'TLS1' value to enforce a STARTTLS connection.
In this mode, it is highly recommended to also use --sslcertck (see
below). Note that this will then cause fetchmail v6.3.19 to force STARTTLS
negotiation even if it is not advertised by the server.
- To defeat opportunistic TLSv1 negotiation when the server advertises
STARTTLS or STLS, and use a cleartext connection use ''. This
option, even if the argument is the empty string, will also suppress the
diagnostic 'SERVER: opportunistic upgrade to TLS.' message in verbose
mode. The default is to try appropriate protocols depending on
context.
- --sslcertck
- (Keyword: sslcertck)
Causes fetchmail to strictly check the server certificate against a set of
local trusted certificates (see the sslcertfile and
sslcertpath options). If the server certificate cannot be obtained
or is not signed by one of the trusted ones (directly or indirectly), the
SSL connection will fail, regardless of the sslfingerprint
option.
- Note that CRL (certificate revocation lists) are only supported in OpenSSL
0.9.7 and newer! Your system clock should also be reasonably accurate when
using this option.
- Note that this optional behavior may become default behavior in future
fetchmail versions.
- --sslcertfile <file>
- (Keyword: sslcertfile, since v6.3.17)
Sets the file fetchmail uses to look up local certificates. The default is
empty. This can be given in addition to --sslcertpath below, and
certificates specified in --sslcertfile will be processed before
those in --sslcertpath. The option can be used in addition to
--sslcertpath.
- The file is a text file. It contains the concatenation of trusted CA
certificates in PEM format.
- Note that using this option will suppress loading the default SSL trusted
CA certificates file unless you set the environment variable
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.
- --sslcertpath <directory>
- (Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates. The default
is your OpenSSL default directory. The directory must be hashed the way
OpenSSL expects it - every time you add or modify a certificate in the
directory, you need to use the c_rehash tool (which comes with
OpenSSL in the tools/ subdirectory). Also, after OpenSSL upgrades, you may
need to run c_rehash; particularly when upgrading from 0.9.X to
1.0.0.
- This can be given in addition to --sslcertfile above, which see for
precedence rules.
- Note that using this option will suppress adding the default SSL trusted
CA certificates directory unless you set the environment variable
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.
- --sslcommonname <common name>
- (Keyword: sslcommonname; since v6.3.9)
Use of this option is discouraged. Before using it, contact the
administrator of your upstream server and ask for a proper SSL certificate
to be used. If that cannot be attained, this option can be used to specify
the name (CommonName) that fetchmail expects on the server certificate. A
correctly configured server will have this set to the hostname by which it
is reached, and by default fetchmail will expect as much. Use this option
when the CommonName is set to some other value, to avoid the "Server
CommonName mismatch" warning, and only if the upstream server can't
be made to use proper certificates.
- --sslfingerprint <fingerprint>
- (Keyword: sslfingerprint)
Specify the fingerprint of the server key (an MD5 hash of the key) in
hexadecimal notation with colons separating groups of two digits. The
letter hex digits must be in upper case. This is the format that fetchmail
uses to report the fingerprint when an SSL connection is established. When
this is specified, fetchmail will compare the server key fingerprint with
the given one, and the connection will fail if they do not match,
regardless of the sslcertck setting. The connection will also fail
if fetchmail cannot obtain an SSL certificate from the server. This can be
used to prevent man-in-the-middle attacks, but the finger print from the
server needs to be obtained or verified over a secure channel, and
certainly not over the same Internet connection that fetchmail would
use.
- Using this option will prevent printing certificate verification errors as
long as --sslcertck is unset.
- To obtain the fingerprint of a certificate stored in the file cert.pem,
try:
openssl x509 -in cert.pem -noout -md5 -fingerprint
For details, see x509(1ssl).
Delivery Control Options¶
- -S <hosts> | --smtphost <hosts>
- (Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more hostnames,
comma-separated). Hosts are tried in list order; the first one that is up
becomes the forwarding target for the current run. If this option is not
specified, 'localhost' is used as the default. Each hostname may have a
port number following the host name. The port number is separated from the
host name by a slash; the default port is "smtp". If you specify
an absolute path name (beginning with a /), it will be interpreted as the
name of a UNIX socket accepting LMTP connections (such as is supported by
the Cyrus IMAP daemon) Example:
--smtphost server1,server2/2525,server3,/var/imap/socket/lmtp
This option can be used with ODMR, and will make fetchmail a relay between
the ODMR server and SMTP or LMTP receiver.
- --fetchdomains <hosts>
- (Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains the server
should ship mail for once the connection is turned around. The default is
the FQDN of the machine running fetchmail.
- -D <domain> | --smtpaddress <domain>
- (Keyword: smtpaddress)
Specify the domain to be appended to addresses in RCPT TO lines shipped to
SMTP. When this is not specified, the name of the SMTP server (as
specified by --smtphost) is used for SMTP/LMTP and 'localhost' is used for
UNIX socket/BSMTP.
- --smtpname <user@domain>
- (Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped to SMTP. The
default user is the current local user.
- -Z <nnn> | --antispam <nnn[, nnn]...>
- (Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be interpreted as a
spam-block response from the listener. A value of -1 disables this option.
For the command-line option, the list values should be
comma-separated.
- -m <command> | --mda <command>
- (Keyword: mda)
This option lets fetchmail use a Message or Local Delivery Agent (MDA
or LDA) directly, rather than forward via SMTP or LMTP.
To avoid losing mail, use this option only with MDAs like maildrop or MTAs
like sendmail that exit with a nonzero status on disk-full and other
delivery errors; the nonzero status tells fetchmail that delivery failed
and prevents the message from being deleted on the server.
If fetchmail is running as root, it sets its user id while delivering
mail through an MDA as follows: First, the FETCHMAILUSER, LOGNAME, and
USER environment variables are checked in this order. The value of the
first variable from his list that is defined (even if it is empty!) is
looked up in the system user database. If none of the variables is
defined, fetchmail will use the real user id it was started with. If one
of the variables was defined, but the user stated there isn't found,
fetchmail continues running as root, without checking remaining variables
on the list. Practically, this means that if you run fetchmail as root
(not recommended), it is most useful to define the FETCHMAILUSER
environment variable to set the user that the MDA should run as. Some MDAs
(such as maildrop) are designed to be setuid root and setuid to the
recipient's user id, so you don't lose functionality this way even when
running fetchmail as unprivileged user. Check the MDA's manual for
details.
Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T" (
Note: some several older or vendor sendmail versions mistake -- for
an address, rather than an indicator to mark the end of the option
arguments), "/usr/bin/deliver" and "/usr/bin/maildrop -d
%T". Local delivery addresses will be inserted into the MDA command
wherever you place a %T; the mail message's From address will be inserted
where you place an %F.
Do NOT enclose the %F or %T string in single quotes! For both %T and
%F, fetchmail encloses the addresses in single quotes ('), after removing
any single quotes they may contain, before the MDA command is passed to
the shell.
Do NOT use an MDA invocation that dispatches on the contents of
To/Cc/Bcc, like "sendmail -i -t" or
"qmail-inject", it will create mail loops and bring the just
wrath of many postmasters down upon your head. This is one of the most
frequent configuration errors!
Also, do not try to combine multidrop mode with an MDA such as
maildrop that can only accept one address, unless your upstream stores one
copy of the message per recipient and transports the envelope recipient in
a header; you will lose mail.
The well-known procmail(1) package is very hard to configure
properly, it has a very nasty "fall through to the next rule"
behavior on delivery errors (even temporary ones, such as out of disk
space if another user's mail daemon copies the mailbox around to purge old
messages), so your mail will end up in the wrong mailbox sooner or later.
The proper procmail configuration is outside the scope of this document.
Using maildrop(1) is usually much easier, and many users find the
filter syntax used by maildrop easier to understand.
Finally, we strongly advise that you do not use qmail-inject. The
command line interface is non-standard without providing benefits for
typical use, and fetchmail makes no attempts to accommodate qmail-inject's
deviations from the standard. Some of qmail-inject's command-line and
environment options are actually dangerous and can cause broken threads,
non-detected duplicate messages and forwarding loops.
- --lmtp
- (Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol). A service host and
port must be explicitly specified on each host in the smtphost hunt
list (see above) if this option is selected; the default port 25 will (in
accordance with RFC 2033) not be accepted.
- --bsmtp <filename>
- (Keyword: bsmtp)
Append fetched mail to a BSMTP file. This simply contains the SMTP commands
that would normally be generated by fetchmail when passing mail to an SMTP
listener daemon.
An argument of '-' causes the SMTP batch to be written to standard output,
which is of limited use: this only makes sense for debugging, because
fetchmail's regular output is interspersed on the same channel, so this
isn't suitable for mail delivery. This special mode may be removed in a
later release.
Note that fetchmail's reconstruction of MAIL FROM and RCPT TO lines is not
guaranteed correct; the caveats discussed under THE USE AND ABUSE OF
MULTIDROP MAILBOXES below apply. This mode has precedence before --mda and
SMTP/LMTP.
- --bad-header {reject|accept}
- (Keyword: bad-header; since v6.3.15)
Specify how fetchmail is supposed to treat messages with bad headers, i. e.
headers with bad syntax. Traditionally, fetchmail has rejected such
messages, but some distributors modified fetchmail to accept them. You can
now configure fetchmail's behaviour per server.
Resource Limit Control Options¶
- -l <maxbytes> | --limit <maxbytes>
- (Keyword: limit)
Takes a maximum octet size argument, where 0 is the default and also the
special value designating "no limit". If nonzero, messages
larger than this size will not be fetched and will be left on the server
(in foreground sessions, the progress messages will note that they are
"oversized"). If the fetch protocol permits (in particular,
under IMAP or POP3 without the fetchall option) the message will not be
marked seen.
An explicit --limit of 0 overrides any limits set in your run control file.
This option is intended for those needing to strictly control fetch time
due to expensive and variable phone rates.
Combined with --limitflush, it can be used to delete oversized messages
waiting on a server. In daemon mode, oversize notifications are mailed to
the calling user (see the --warnings option). This option does not work
with ETRN or ODMR.
- -w <interval> | --warnings <interval>
- (Keyword: warnings)
Takes an interval in seconds. When you call fetchmail with a 'limit'
option in daemon mode, this controls the interval at which warnings about
oversized messages are mailed to the calling user (or the user specified
by the 'postmaster' option). One such notification is always mailed at the
end of the the first poll that the oversized message is detected.
Thereafter, re-notification is suppressed until after the warning interval
elapses (it will take place at the end of the first following poll).
- -b <count> | --batchlimit <count>
- (Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to an SMTP
listener before the connection is deliberately torn down and rebuilt
(defaults to 0, meaning no limit). An explicit --batchlimit of 0 overrides
any limits set in your run control file. While sendmail(8) normally
initiates delivery of a message immediately after receiving the message
terminator, some SMTP listeners are not so prompt. MTAs like
smail(8) may wait till the delivery socket is shut down to deliver.
This may produce annoying delays when fetchmail is processing very
large batches. Setting the batch limit to some nonzero size will prevent
these delays. This option does not work with ETRN or ODMR.
- -B <number> | --fetchlimit <number>
- (Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a single poll.
By default there is no limit. An explicit --fetchlimit of 0 overrides any
limits set in your run control file. This option does not work with ETRN
or ODMR.
- --fetchsizelimit <number>
- (Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given server in a
single transaction. This option is useful in reducing the delay in
downloading the first mail when there are too many mails in the mailbox.
By default, the limit is 100. If set to 0, sizes of all messages are
downloaded at the start. This option does not work with ETRN or ODMR. For
POP3, the only valid non-zero value is 1.
- --fastuidl <number>
- (Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID. Binary search
avoids downloading the UIDs of all mails. This saves time (especially in
daemon mode) where downloading the same set of UIDs in each poll is a
waste of bandwidth. The number 'n' indicates how rarely a linear search
should be done. In daemon mode, linear search is used once followed by
binary searches in 'n-1' polls if 'n' is greater than 1; binary search is
always used if 'n' is 1; linear search is always used if 'n' is 0. In
non-daemon mode, binary search is used if 'n' is 1; otherwise linear
search is used. The default value of 'n' is 4. This option works with POP3
only.
- -e <count> | --expunge <count>
- (Keyword: expunge)
Arrange for deletions to be made final after a given number of messages.
Under POP2 or POP3, fetchmail cannot make deletions final without sending
QUIT and ending the session -- with this option on, fetchmail will break a
long mail retrieval session into multiple sub-sessions, sending QUIT after
each sub-session. This is a good defense against line drops on POP3
servers. Under IMAP, fetchmail normally issues an EXPUNGE command
after each deletion in order to force the deletion to be done immediately.
This is safest when your connection to the server is flaky and expensive,
as it avoids resending duplicate mail after a line hit. However, on large
mailboxes the overhead of re-indexing after every message can slam the
server pretty hard, so if your connection is reliable it is good to do
expunges less frequently. Also note that some servers enforce a delay of a
few seconds after each quit, so fetchmail may not be able to get back in
immediately after an expunge -- you may see "lock busy" errors
if this happens. If you specify this option to an integer N, it tells
fetchmail to only issue expunges on every Nth delete. An argument
of zero suppresses expunges entirely (so no expunges at all will be done
until the end of run). This option does not work with ETRN or ODMR.
Authentication Options¶
- -u <name> | --user <name> | --username
<name>
- (Keyword: user[name])
Specifies the user identification to be used when logging in to the
mailserver. The appropriate user identification is both server and
user-dependent. The default is your login name on the client machine that
is running fetchmail. See USER AUTHENTICATION below for a complete
description.
- -I <specification> | --interface <specification>
- (Keyword: interface)
Require that a specific interface device be up and have a specific local or
remote IPv4 (IPv6 is not supported by this option yet) address (or range)
before polling. Frequently fetchmail is used over a transient
point-to-point TCP/IP link established directly to a mailserver via SLIP
or PPP. That is a relatively secure channel. But when other TCP/IP routes
to the mailserver exist (e.g. when the link is connected to an alternate
ISP), your username and password may be vulnerable to snooping (especially
when daemon mode automatically polls for mail, shipping a clear password
over the net at predictable intervals). The --interface option may be used
to prevent this. When the specified link is not up or is not connected to
a matching IP address, polling will be skipped. The format is:
interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]
The field before the first slash is the interface name (i.e. sl0, ppp0
etc.). The field before the second slash is the acceptable IP address. The
field after the second slash is a mask which specifies a range of IP
addresses to accept. If no mask is present 255.255.255.255 is assumed
(i.e. an exact match). This option is currently only supported under Linux
and FreeBSD. Please see the monitor section for below for FreeBSD
specific information.
Note that this option may be removed from a future fetchmail version.
- -M <interface> | --monitor <interface>
- (Keyword: monitor)
Daemon mode can cause transient links which are automatically taken down
after a period of inactivity (e.g. PPP links) to remain up indefinitely.
This option identifies a system TCP/IP interface to be monitored for
activity. After each poll interval, if the link is up but no other
activity has occurred on the link, then the poll will be skipped. However,
when fetchmail is woken up by a signal, the monitor check is skipped and
the poll goes through unconditionally. This option is currently only
supported under Linux and FreeBSD. For the monitor and
interface options to work for non root users under FreeBSD, the
fetchmail binary must be installed SGID kmem. This would be a security
hole, but fetchmail runs with the effective GID set to that of the kmem
group only when interface data is being collected.
Note that this option may be removed from a future fetchmail version.
- --auth <type>
- (Keyword: auth[enticate])
This option permits you to specify an authentication type (see USER
AUTHENTICATION below for details). The possible values are any,
password, kerberos_v5, kerberos (or, for excruciating
exactness, kerberos_v4), gssapi, cram-md5,
otp, ntlm, msn (only for POP3), external (only
IMAP) and ssh. When any (the default) is specified,
fetchmail tries first methods that don't require a password (EXTERNAL,
GSSAPI, KERBEROS IV, KERBEROS 5); then it looks for methods
that mask your password (CRAM-MD5, NTLM, X-OTP - note that MSN is only
supported for POP3, but not autoprobed); and only if the server doesn't
support any of those will it ship your password en clair. Other values may
be used to force various authentication methods ( ssh suppresses
authentication and is thus useful for IMAP PREAUTH). ( external
suppresses authentication and is thus useful for IMAP EXTERNAL). Any value
other than password, cram-md5, ntlm, msn or
otp suppresses fetchmail's normal inquiry for a password. Specify
ssh when you are using an end-to-end secure connection such as an
ssh tunnel; specify external when you use TLS with client
authentication and specify gssapi or kerberos_v4 if you are
using a protocol variant that employs GSSAPI or K4. Choosing KPOP protocol
automatically selects Kerberos authentication. This option does not work
with ETRN. GSSAPI service names are in line with RFC-2743 and IANA
registrations, see
Miscellaneous Options¶
- -f <pathname> | --fetchmailrc <pathname>
- Specify a non-default name for the ~/.fetchmailrc run control file.
The pathname argument must be either "-" (a single dash, meaning
to read the configuration from standard input) or a filename. Unless the
--version option is also on, a named file argument must have permissions
no more open than 0700 (u=rwx,g=,o=) or else be /dev/null.
- -i <pathname> | --idfile <pathname>
- (Keyword: idfile)
Specify an alternate name for the .fetchids file used to save message UIDs.
NOTE: since fetchmail 6.3.0, write access to the directory containing the
idfile is required, as fetchmail writes a temporary file and renames it
into the place of the real idfile only if the temporary file has been
written successfully. This avoids the truncation of idfiles when running
out of disk space.
- --pidfile <pathname>
- (Keyword: pidfile; since fetchmail v6.3.4)
Override the default location of the PID file. Default: see
"ENVIRONMENT" below.
- -n | --norewrite
- (Keyword: no rewrite)
Normally, fetchmail edits RFC-822 address headers (To, From, Cc, Bcc,
and Reply-To) in fetched mail so that any mail IDs local to the server are
expanded to full addresses (@ and the mailserver hostname are appended).
This enables replies on the client to get addressed correctly (otherwise
your mailer might think they should be addressed to local users on the
client machine!). This option disables the rewrite. (This option is
provided to pacify people who are paranoid about having an MTA edit mail
headers and want to know they can prevent it, but it is generally not a
good idea to actually turn off rewrite.) When using ETRN or ODMR, the
rewrite option is ineffective.
- -E <line> | --envelope <line>
- (Keyword: envelope; Multidrop only)
In the configuration file, an enhanced syntax is used:
envelope [<count>] <line>
This option changes the header fetchmail assumes will carry a copy of
the mail's envelope address. Normally this is 'X-Envelope-To'. Other
typically found headers to carry envelope information are 'X-Original-To'
and 'Delivered-To'. Now, since these headers are not standardized,
practice varies. See the discussion of multidrop address handling below.
As a special case, 'envelope "Received"' enables parsing of
sendmail-style Received lines. This is the default, but discouraged
because it is not fully reliable.
Note that fetchmail expects the Received-line to be in a specific format: It
must contain "by host for address", where
host must match one of the mailserver names that fetchmail
recognizes for the account in question.
The optional count argument (only available in the configuration file)
determines how many header lines of this kind are skipped. A count of 1
means: skip the first, take the second. A count of 2 means: skip the first
and second, take the third, and so on.
- -Q <prefix> | --qvirtual <prefix>
- (Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from the user name
found in the header specified with the envelope option (
before doing multidrop name mapping or localdomain checking, if
either is applicable). This option is useful if you are using
fetchmail to collect the mail for an entire domain and your ISP (or
your mail redirection provider) is using qmail. One of the basic features
of qmail is the Delivered-To: message header. Whenever qmail
delivers a message to a local mailbox it puts the username and hostname of
the envelope recipient on this line. The major reason for this is to
prevent mail loops. To set up qmail to batch mail for a disconnected site
the ISP-mailhost will have normally put that site in its 'Virtualhosts'
control file so it will add a prefix to all mail addresses for this site.
This results in mail sent to 'username@userhost.userdom.dom.com' having a
Delivered-To: line of the form:
- Delivered-To: mbox-userstr-username@userhost.example.com
The ISP can make the 'mbox-userstr-' prefix anything they choose but a string
matching the user host name is likely. By using the option 'envelope
Delivered-To:' you can make fetchmail reliably identify the original envelope
recipient, but you have to strip the 'mbox-userstr-' prefix to deliver to the
correct user. This is what this option is for.
- --configdump
- Parse the ~/.fetchmailrc file, interpret any command-line options
specified, and dump a configuration report to standard output. The
configuration report is a data structure assignment in the language
Python. This option is meant to be used with an interactive
~/.fetchmailrc editor like fetchmailconf, written in Python.
Removed Options¶
- -T | --netsec
- Removed before version 6.3.0, the required underlying inet6_apps library
had been discontinued and is no longer available.
USER AUTHENTICATION AND ENCRYPTION¶
All modes except ETRN require authentication of the client to the server. Normal
user authentication in
fetchmail is very much like the authentication
mechanism of
ftp(1). The correct user-id and password depend upon the
underlying security system at the mailserver.
If the mailserver is a Unix machine on which you have an ordinary user account,
your regular login name and password are used with
fetchmail. If you
use the same login name on both the server and the client machines, you
needn't worry about specifying a user-id with the
-u option -- the
default behavior is to use your login name on the client machine as the
user-id on the server machine. If you use a different login name on the server
machine, specify that login name with the
-u option. e.g. if your login
name is 'jsmith' on a machine named 'mailgrunt', you would start
fetchmail as follows:
- fetchmail -u jsmith mailgrunt
The default behavior of
fetchmail is to prompt you for your mailserver
password before the connection is established. This is the safest way to use
fetchmail and ensures that your password will not be compromised. You
may also specify your password in your
~/.fetchmailrc file. This is
convenient when using
fetchmail in daemon mode or with scripts.
Using netrc files¶
If you do not specify a password, and
fetchmail cannot extract one from
your
~/.fetchmailrc file, it will look for a
~/.netrc file in
your home directory before requesting one interactively; if an entry matching
the mailserver is found in that file, the password will be used. Fetchmail
first looks for a match on poll name; if it finds none, it checks for a match
on via name. See the
ftp(1) man page for details of the syntax of the
~/.netrc file. To show a practical example, a .netrc might look like
this:
-
machine hermes.example.org
login joe
password topsecret
You can repeat this block with different user information if you need to provide
more than one password.
This feature may allow you to avoid duplicating password information in more
than one file.
On mailservers that do not provide ordinary user accounts, your user-id and
password are usually assigned by the server administrator when you apply for a
mailbox on the server. Contact your server administrator if you don't know the
correct user-id and password for your mailbox account.
POP3 VARIANTS¶
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of independent
authentication using the
.rhosts file on the mailserver side. Under
this RPOP variant, a fixed per-user ID equivalent to a password was sent in
clear over a link to a reserved port, with the command RPOP rather than PASS
to alert the server that it should do special checking. RPOP is supported by
fetchmail (you can specify 'protocol RPOP' to have the program send
'RPOP' rather than 'PASS') but its use is strongly discouraged, and support
will be removed from a future fetchmail version. This facility was vulnerable
to spoofing and was withdrawn in RFC1460.
RFC1460 introduced APOP authentication. In this variant of POP3, you register an
APOP password on your server host (on some servers, the program to do this is
called
popauth(8)). You put the same password in your
~/.fetchmailrc file. Each time
fetchmail logs in, it sends an
MD5 hash of your password and the server greeting time to the server, which
can verify it by checking its authorization database.
Note that APOP is no longer considered resistant against
man-in-the-middle attacks.
RETR or TOP¶
fetchmail makes some efforts to make the server believe messages had not
been retrieved, by using the TOP command with a large number of lines when
possible. TOP is a command that retrieves the full header and a
fetchmail-specified amount of body lines. It is optional and therefore
not implemented by all servers, and some are known to implement it improperly.
On many servers however, the RETR command which retrieves the full message
with header and body, sets the "seen" flag (for instance, in a web
interface), whereas the TOP command does not do that.
fetchmail will always use the RETR command if "fetchall" is
set.
fetchmail will also use the RETR command if "keep" is
set and "uidl" is unset. Finally,
fetchmail will use the RETR
command on Maillennium POP3/PROXY servers (used by Comcast) to avoid a
deliberate TOP misinterpretation in this server that causes message
corruption.
In all other cases,
fetchmail will use the TOP command. This implies that
in "keep" setups, "uidl" must be set if "TOP" is
desired.
Note that this description is true for the current version of fetchmail,
but the behavior may change in future versions. In particular, fetchmail may
prefer the RETR command because the TOP command causes much grief on some
servers and is only optional.
If your
fetchmail was built with Kerberos support and you specify
Kerberos authentication (either with --auth or the
.fetchmailrc option
authenticate kerberos_v4) it will try to get a Kerberos ticket from the
mailserver at the start of each query. Note: if either the pollname or via
name is 'hesiod', fetchmail will try to use Hesiod to look up the mailserver.
If you use POP3 or IMAP with GSSAPI authentication,
fetchmail will expect
the server to have RFC1731- or RFC1734-conforming GSSAPI capability, and will
use it. Currently this has only been tested over Kerberos V, so you're
expected to already have a ticket-granting ticket. You may pass a username
different from your principal name using the standard
--user command or
by the
.fetchmailrc option
user.
If your IMAP daemon returns the PREAUTH response in its greeting line, fetchmail
will notice this and skip the normal authentication step. This can be useful,
e.g. if you start imapd explicitly using ssh. In this case you can declare the
authentication value 'ssh' on that site entry to stop
.fetchmail from
asking you for a password when it starts up.
If you use client authentication with
TLS1 and your IMAP daemon returns
the
AUTH=EXTERNAL response, fetchmail will notice this and will use the
authentication shortcut and will not send the passphrase. In this case you can
declare the authentication value 'external'
on that site to stop
fetchmail from asking you for a password when it
starts up.
If you are using POP3, and the server issues a one-time-password challenge
conforming to RFC1938,
fetchmail will use your password as a pass
phrase to generate the required response. This avoids sending secrets over the
net unencrypted.
Compuserve's RPA authentication is supported. If you compile in the support,
fetchmail will try to perform an RPA pass-phrase authentication instead
of sending over the password en clair if it detects
"@compuserve.com" in the hostname.
If you are using IMAP, Microsoft's NTLM authentication (used by Microsoft
Exchange) is supported. If you compile in the support,
fetchmail will
try to perform an NTLM authentication (instead of sending over the password en
clair) whenever the server returns AUTH=NTLM in its capability response.
Specify a user option value that looks like 'user@domain': the part to the
left of the @ will be passed as the username and the part to the right as the
NTLM domain.
Secure Socket Layers (SSL) and Transport Layer Security (TLS)¶
Note that fetchmail currently uses the OpenSSL library, which is severely
underdocumented, so failures may occur just because the programmers are not
aware of OpenSSL's requirement of the day. For instance, since v6.3.16,
fetchmail calls OpenSSL_add_all_algorithms(), which is necessary to support
certificates using SHA256 on OpenSSL 0.9.8 -- this information is deeply
hidden in the documentation and not at all obvious. Please do not hesitate to
report subtle SSL failures.
You can access SSL encrypted services by specifying the --ssl option. You can
also do this using the "ssl" user option in the .fetchmailrc file.
With SSL encryption enabled, queries are initiated over a connection after
negotiating an SSL session, and the connection fails if SSL cannot be
negotiated. Some services, such as POP3 and IMAP, have different well known
ports defined for the SSL encrypted services. The encrypted ports will be
selected automatically when SSL is enabled and no explicit port is specified.
The --sslproto 'SSL3' option should be used to select the SSLv3 protocol
(default if unset: v2 or v3). Also, the --sslcertck command line or sslcertck
run control file option should be used to force strict certificate checking -
see below.
If SSL is not configured, fetchmail will usually opportunistically try to use
STARTTLS. STARTTLS can be enforced by using --sslproto "TLS1". TLS
connections use the same port as the unencrypted version of the protocol and
negotiate TLS via special command. The --sslcertck command line or sslcertck
run control file option should be used to force strict certificate checking -
see below.
--sslcertck is recommended: When connecting to an SSL or TLS encrypted
server, the server presents a certificate to the client for validation. The
certificate is checked to verify that the common name in the certificate
matches the name of the server being contacted and that the effective and
expiration dates in the certificate indicate that it is currently valid. If
any of these checks fail, a warning message is printed, but the connection
continues. The server certificate does not need to be signed by any specific
Certifying Authority and may be a "self-signed" certificate. If the
--sslcertck command line option or sslcertck run control file option is used,
fetchmail will instead abort if any of these checks fail, because it must
assume that there is a man-in-the-middle attack in this scenario, hence
fetchmail must not expose cleartext passwords. Use of the sslcertck or
--sslcertck option is therefore advised.
Some SSL encrypted servers may request a client side certificate. A client side
public SSL certificate and private SSL key may be specified. If requested by
the server, the client certificate is sent to the server for validation. Some
servers may require a valid client certificate and may refuse connections if a
certificate is not provided or if the certificate is not valid. Some servers
may require client side certificates be signed by a recognized Certifying
Authority. The format for the key files and the certificate files is that
required by the underlying SSL libraries (OpenSSL in the general case).
A word of care about the use of SSL: While above mentioned setup with
self-signed server certificates retrieved over the wires can protect you from
a passive eavesdropper, it doesn't help against an active attacker. It's
clearly an improvement over sending the passwords in clear, but you should be
aware that a man-in-the-middle attack is trivially possible (in particular
with tools such as ). Use of strict certificate checking with a certification
authority recognized by server and client, or perhaps of an SSH tunnel (see
below for some examples) is preferable if you care seriously about the
security of your mailbox and passwords.
ESMTP AUTH¶
fetchmail also supports authentication to the ESMTP server on the client
side according to RFC 2554. You can specify a name/password pair to be used
with the keywords 'esmtpname' and 'esmtppassword'; the former defaults to the
username of the calling user.
DAEMON MODE¶
Introducing the daemon mode¶
In daemon mode,
fetchmail puts itself into the background and runs
forever, querying each specified host and then sleeping for a given polling
interval.
Starting the daemon mode¶
There are several ways to make fetchmail work in daemon mode. On the command
line,
--daemon <interval> or
-d <interval> option runs
fetchmail in daemon mode.
You must specify a numeric argument which is a polling interval (time to wait
after completing a whole poll cycle with the last server and before starting
the next poll cycle with the first server) in seconds.
Example: simply invoking
- fetchmail -d 900
will, therefore, poll all the hosts described in your
~/.fetchmailrc file
(except those explicitly excluded with the 'skip' verb) a bit less often than
once every 15 minutes (exactly: 15 minutes + time that the poll takes).
It is also possible to set a polling interval in your
~/.fetchmailrc file
by saying 'set daemon <interval>', where <interval>
is an integer number of seconds. If you do this, fetchmail will always start
in daemon mode unless you override it with the command-line option --daemon 0
or -d0.
Only one daemon process is permitted per user; in daemon mode,
fetchmail
sets up a per-user lockfile to guarantee this. (You can however cheat and set
the FETCHMAILHOME environment variable to overcome this setting, but in that
case, it is your responsibility to make sure you aren't polling the same
server with two processes at the same time.)
Awakening the background daemon¶
Normally, calling fetchmail with a daemon in the background sends a wake-up
signal to the daemon and quits without output. The background daemon then
starts its next poll cycle immediately. The wake-up signal, SIGUSR1, can also
be sent manually. The wake-up action also clears any 'wedged' flags indicating
that connections have wedged due to failed authentication or multiple
timeouts.
Terminating the background daemon¶
The option
--quit will kill a running daemon process instead of waking it
up (if there is no such process,
fetchmail will notify you). If the
--quit option appears last on the command line,
fetchmail will kill the
running daemon process and then quit. Otherwise,
fetchmail will first
kill a running daemon process and then continue running with the other
options.
Useful options for daemon mode¶
The
-L <filename> or
--logfile <filename> option
(keyword: set logfile) is only effective when fetchmail is detached and in
daemon mode. Note that
the logfile must exist before fetchmail
is run, you can use the
touch(1) command with the filename as its sole
argument to create it.
This option allows you to redirect status messages into a specified logfile
(follow the option with the logfile name). The logfile is opened for append,
so previous messages aren't deleted. This is primarily useful for debugging
configurations. Note that fetchmail does not detect if the logfile is rotated,
the logfile is only opened once when fetchmail starts. You need to restart
fetchmail after rotating the logfile and before compressing it (if
applicable).
The
--syslog option (keyword: set syslog) allows you to redirect status
and error messages emitted to the
syslog(3) system daemon if available.
Messages are logged with an id of
fetchmail, the facility
LOG_MAIL, and priorities
LOG_ERR,
LOG_ALERT or
LOG_INFO. This option is intended for logging status and error messages
which indicate the status of the daemon and the results while fetching mail
from the server(s). Error messages for command line options and parsing the
.fetchmailrc file are still written to stderr, or to the specified log
file. The
--nosyslog option turns off use of
syslog(3), assuming
it's turned on in the
~/.fetchmailrc file. This option is overridden,
in certain situations, by
--logfile (which see).
The
-N or
--nodetach option suppresses backgrounding and
detachment of the daemon process from its control terminal. This is useful for
debugging or when fetchmail runs as the child of a supervisor process such as
init(8) or Gerrit Pape's
runit(8). Note that this also causes
the logfile option to be ignored.
Note that while running in daemon mode polling a POP2 or IMAP2bis server,
transient errors (such as DNS failures or sendmail delivery refusals) may
force the fetchall option on for the duration of the next polling cycle. This
is a robustness feature. It means that if a message is fetched (and thus
marked seen by the mailserver) but not delivered locally due to some transient
error, it will be re-fetched during the next poll cycle. (The IMAP logic
doesn't delete messages until they're delivered, so this problem does not
arise.)
If you touch or change the
~/.fetchmailrc file while fetchmail is running
in daemon mode, this will be detected at the beginning of the next poll cycle.
When a changed
~/.fetchmailrc is detected, fetchmail rereads it and
restarts from scratch (using exec(2); no state information is retained in the
new instance). Note that if fetchmail needs to query for passwords, of that if
you break the
~/.fetchmailrc file's syntax, the new instance will
softly and silently vanish away on startup.
ADMINISTRATIVE OPTIONS¶
The
--postmaster <name> option (keyword: set postmaster) specifies
the last-resort username to which multidrop mail is to be forwarded if no
matching local recipient can be found. It is also used as destination of
undeliverable mail if the 'bouncemail' global option is off and additionally
for spam-blocked mail if the 'bouncemail' global option is off and the
'spambounce' global option is on. This option defaults to the user who invoked
fetchmail. If the invoking user is root, then the default of this
option is the user 'postmaster'. Setting postmaster to the empty string causes
such mail as described above to be discarded - this however is usually a bad
idea. See also the description of the 'FETCHMAILUSER' environment variable in
the ENVIRONMENT section below.
The
--nobounce behaves like the "set no bouncemail" global
option, which see.
The
--invisible option (keyword: set invisible) tries to make fetchmail
invisible. Normally, fetchmail behaves like any other MTA would -- it
generates a Received header into each message describing its place in the
chain of transmission, and tells the MTA it forwards to that the mail came
from the machine fetchmail itself is running on. If the invisible option is
on, the Received header is suppressed and fetchmail tries to spoof the MTA it
forwards to into thinking it came directly from the mailserver host.
The
--showdots option (keyword: set showdots) forces fetchmail to show
progress dots even if the output goes to a file or fetchmail is not in verbose
mode. Fetchmail shows the dots by default when run in --verbose mode
and output goes to console. This option is ignored in --silent mode.
By specifying the
--tracepolls option, you can ask fetchmail to add
information to the Received header on the form "polling {label} account
{user}", where {label} is the account label (from the specified rcfile,
normally ~/.fetchmailrc) and {user} is the username which is used to log on to
the mail server. This header can be used to make filtering email where no
useful header information is available and you want mail from different
accounts sorted into different mailboxes (this could, for example, occur if
you have an account on the same server running a mailing list, and are
subscribed to the list using that account). The default is not adding any such
header. In
.fetchmailrc, this is called 'tracepolls'.
RETRIEVAL FAILURE MODES¶
The protocols
fetchmail uses to talk to mailservers are next to
bulletproof. In normal operation forwarding to port 25, no message is ever
deleted (or even marked for deletion) on the host until the SMTP listener on
the client side has acknowledged to
fetchmail that the message has been
either accepted for delivery or rejected due to a spam block.
When forwarding to an MDA, however, there is more possibility of error. Some
MDAs are 'safe' and reliably return a nonzero status on any delivery error,
even one due to temporary resource limits. The
maildrop(1) program is
like this; so are most programs designed as mail transport agents, such as
sendmail(1), including the sendmail wrapper of Postfix and
exim(1). These programs give back a reliable positive acknowledgement
and can be used with the mda option with no risk of mail loss. Unsafe MDAs,
though, may return 0 even on delivery failure. If this happens, you will lose
mail.
The normal mode of
fetchmail is to try to download only 'new' messages,
leaving untouched (and undeleted) messages you have already read directly on
the server (or fetched with a previous
fetchmail --keep). But
you may find that messages you've already read on the server are being fetched
(and deleted) even when you don't specify --all. There are several reasons
this can happen.
One could be that you're using POP2. The POP2 protocol includes no
representation of 'new' or 'old' state in messages, so
fetchmail must
treat all messages as new all the time. But POP2 is obsolete, so this is
unlikely.
A potential POP3 problem might be servers that insert messages in the middle of
mailboxes (some VMS implementations of mail are rumored to do this). The
fetchmail code assumes that new messages are appended to the end of the
mailbox; when this is not true it may treat some old messages as new and vice
versa. Using UIDL whilst setting fastuidl 0 might fix this, otherwise,
consider switching to IMAP.
Yet another POP3 problem is that if they can't make tempfiles in the user's home
directory, some POP3 servers will hand back an undocumented response that
causes fetchmail to spuriously report "No mail".
The IMAP code uses the presence or absence of the server flag \Seen to decide
whether or not a message is new. This isn't the right thing to do, fetchmail
should check the UIDVALIDITY and use UID, but it doesn't do that yet. Under
Unix, it counts on your IMAP server to notice the BSD-style Status flags set
by mail user agents and set the \Seen flag from them when appropriate. All
Unix IMAP servers we know of do this, though it's not specified by the IMAP
RFCs. If you ever trip over a server that doesn't, the symptom will be that
messages you have already read on your host will look new to the server. In
this (unlikely) case, only messages you fetched with
fetchmail --keep
will be both undeleted and marked old.
In ETRN and ODMR modes,
fetchmail does not actually retrieve messages;
instead, it asks the server's SMTP listener to start a queue flush to the
client via SMTP. Therefore it sends only undelivered messages.
SPAM FILTERING¶
Many SMTP listeners allow administrators to set up 'spam filters' that block
unsolicited email from specified domains. A MAIL FROM or DATA line that
triggers this feature will elicit an SMTP response which (unfortunately)
varies according to the listener.
Newer versions of
sendmail return an error code of 571.
According to RFC2821, the correct thing to return in this situation is 550
"Requested action not taken: mailbox unavailable" (the draft adds
"[E.g., mailbox not found, no access, or command rejected for policy
reasons].").
Older versions of the
exim MTA return 501 "Syntax error in
parameters or arguments".
The
postfix MTA runs 554 as an antispam response.
Zmailer may reject code with a 500 response (followed by an enhanced
status code that contains more information).
Return codes which
fetchmail treats as antispam responses and discards
the message can be set with the 'antispam' option. This is one of the
only three circumstance under which fetchmail ever discards mail (the
others are the 552 and 553 errors described below, and the suppression of
multidropped messages with a message-ID already seen).
If
fetchmail is fetching from an IMAP server, the antispam response will
be detected and the message rejected immediately after the headers have been
fetched, without reading the message body. Thus, you won't pay for downloading
spam message bodies.
By default, the list of antispam responses is empty.
If the
spambounce global option is on, mail that is spam-blocked triggers
an RFC1892/RFC1894 bounce message informing the originator that we do not
accept mail from it. See also BUGS.
SMTP/ESMTP ERROR HANDLING¶
Besides the spam-blocking described above, fetchmail takes special actions
— that may be modified by the --softbounce option — on the
following SMTP/ESMTP error response codes
- 452 (insufficient system storage)
- Leave the message in the server mailbox for later retrieval.
- 552 (message exceeds fixed maximum message size)
- Delete the message from the server. Send bounce-mail to the
originator.
- 553 (invalid sending domain)
- Delete the message from the server. Don't even try to send bounce-mail to
the originator.
Other errors greater or equal to 500 trigger bounce mail back to the originator,
unless suppressed by --softbounce. See also BUGS.
THE RUN CONTROL FILE¶
The preferred way to set up fetchmail is to write a
.fetchmailrc file in
your home directory (you may do this directly, with a text editor, or
indirectly via
fetchmailconf). When there is a conflict between the
command-line arguments and the arguments in this file, the command-line
arguments take precedence.
To protect the security of your passwords, your
~/.fetchmailrc may not
normally have more than 0700 (u=rwx,g=,o=) permissions;
fetchmail will
complain and exit otherwise (this check is suppressed when --version is on).
You may read the
.fetchmailrc file as a list of commands to be executed
when
fetchmail is called with no arguments.
Run Control Syntax¶
Comments begin with a '#' and extend through the end of the line. Otherwise the
file consists of a series of server entries or global option statements in a
free-format, token-oriented syntax.
There are four kinds of tokens: grammar keywords, numbers (i.e. decimal digit
sequences), unquoted strings, and quoted strings. A quoted string is bounded
by double quotes and may contain whitespace (and quoted digits are treated as
a string). Note that quoted strings will also contain line feed characters if
they run across two or more lines, unless you use a backslash to join lines
(see below). An unquoted string is any whitespace-delimited token that is
neither numeric, string quoted nor contains the special characters ',', ';',
':', or '='.
Any amount of whitespace separates tokens in server entries, but is otherwise
ignored. You may use backslash escape sequences (\n for LF, \t for HT, \b for
BS, \r for CR, \
nnn for decimal (where nnn cannot start with a 0), \0
ooo for octal, and \x
hh for hex) to embed non-printable
characters or string delimiters in strings. In quoted strings, a backslash at
the very end of a line will cause the backslash itself and the line feed (LF
or NL, new line) character to be ignored, so that you can wrap long strings.
Without the backslash at the line end, the line feed character would become
part of the string.
Warning: while these resemble C-style escape sequences, they are not the
same. fetchmail only supports these eight styles. C supports more escape
sequences that consist of backslash (\) and a single character, but does not
support decimal codes and does not require the leading 0 in octal notation.
Example: fetchmail interprets \233 the same as \xE9 (Latin small letter e with
acute), where C would interpret \233 as octal 0233 = \x9B (CSI, control
sequence introducer).
Each server entry consists of one of the keywords 'poll' or 'skip', followed by
a server name, followed by server options, followed by any number of user (or
username) descriptions, followed by user options. Note: the most common cause
of syntax errors is mixing up user and server options or putting user options
before the user descriptions.
For backward compatibility, the word 'server' is a synonym for 'poll'.
You can use the noise keywords 'and', 'with', 'has', 'wants', and 'options'
anywhere in an entry to make it resemble English. They're ignored, but but can
make entries much easier to read at a glance. The punctuation characters ':',
';' and ',' are also ignored.
Poll vs. Skip¶
The 'poll' verb tells fetchmail to query this host when it is run with no
arguments. The 'skip' verb tells
fetchmail not to poll this host unless
it is explicitly named on the command line. (The 'skip' verb allows you to
experiment with test entries safely, or easily disable entries for hosts that
are temporarily down.)
Keyword/Option Summary¶
Here are the legal options. Keyword suffixes enclosed in square brackets are
optional. Those corresponding to short command-line options are followed by
'-' and the appropriate option letter. If option is only relevant to a single
mode of operation, it is noted as 's' or 'm' for singledrop- or
multidrop-mode, respectively.
Here are the legal global options:
Keyword |
Opt |
Mode |
Function |
|
set daemon |
-d |
|
Set a background poll interval in seconds. |
set postmaster |
|
|
Give the name of the last-resort mail recipient (default: user running
fetchmail, "postmaster" if run by the root user) |
set bouncemail |
|
|
Direct error mail to the sender (default) |
set no bouncemail |
|
|
Direct error mail to the local postmaster (as per the 'postmaster'
global option above). |
set no spambounce |
|
|
Do not bounce spam-blocked mail (default). |
set spambounce |
|
|
Bounce blocked spam-blocked mail (as per the 'antispam' user option)
back to the destination as indicated by the 'bouncemail' global option.
Warning: Do not use this to bounce spam back to the sender - most spam is
sent with false sender address and thus this option hurts innocent
bystanders. |
set no softbounce |
|
|
Delete permanently undeliverable mail. It is recommended to use this
option if the configuration has been thoroughly tested. |
set softbounce |
|
|
Keep permanently undeliverable mail as though a temporary error had
occurred (default). |
set logfile |
-L |
|
Name of a file to append error and status messages to. Only effective in
daemon mode and if fetchmail detaches. If effective, overrides set
syslog. |
set idfile |
-i |
|
Name of the file to store UID lists in. |
set syslog |
|
|
Do error logging through syslog(3). May be overriden by set
logfile. |
set no syslog |
|
|
Turn off error logging through syslog(3). (default) |
set properties |
|
|
String value that is ignored by fetchmail (may be used by extension
scripts). |
Here are the legal server options:
Keyword |
Opt |
Mode |
Function |
|
via |
|
|
Specify DNS name of mailserver, overriding poll name |
proto[col] |
-p |
|
Specify protocol (case insensitive): POP2, POP3, IMAP, APOP, KPOP |
local[domains] |
|
m |
Specify domain(s) to be regarded as local |
port |
|
|
Specify TCP/IP service port (obsolete, use 'service' instead). |
service |
-P |
|
Specify service name (a numeric value is also allowed and considered a
TCP/IP port number). |
auth[enticate] |
|
|
Set authentication type (default 'any') |
timeout |
-t |
|
Server inactivity timeout in seconds (default 300) |
envelope |
-E |
m |
Specify envelope-address header name |
no envelope |
|
m |
Disable looking for envelope address |
qvirtual |
-Q |
m |
Qmail virtual domain prefix to remove from user name |
aka |
|
m |
Specify alternate DNS names of mailserver |
interface |
-I |
|
specify IP interface(s) that must be up for server poll to take
place |
monitor |
-M |
|
Specify IP address to monitor for activity |
plugin |
|
|
Specify command through which to make server connections. |
plugout |
|
|
Specify command through which to make listener connections. |
dns |
|
m |
Enable DNS lookup for multidrop (default) |
no dns |
|
m |
Disable DNS lookup for multidrop |
checkalias |
|
m |
Do comparison by IP address for multidrop |
no checkalias |
|
m |
Do comparison by name for multidrop (default) |
uidl |
-U |
|
Force POP3 to use client-side UIDLs (recommended) |
no uidl |
|
|
Turn off POP3 use of client-side UIDLs (default) |
interval |
|
|
Only check this site every N poll cycles; N is a numeric argument. |
tracepolls |
|
|
Add poll tracing information to the Received header |
principal |
|
|
Set Kerberos principal (only useful with IMAP and kerberos) |
esmtpname |
|
|
Set name for RFC2554 authentication to the ESMTP server. |
esmtppassword |
|
|
Set password for RFC2554 authentication to the ESMTP server. |
bad-header |
|
|
How to treat messages with a bad header. Can be reject (default) or
accept. |
Here are the legal user descriptions and options:
Keyword |
Opt |
Mode |
Function |
|
user[name] |
-u |
|
This is the user description and must come first after server
description and after possible server options, and before user options. It
sets the remote user name if by itself or followed by 'there', or the
local user name if followed by 'here'. |
is |
|
|
Connect local and remote user names |
to |
|
|
Connect local and remote user names |
pass[word] |
|
|
Specify remote account password |
ssl |
|
|
Connect to server over the specified base protocol using SSL
encryption |
sslcert |
|
|
Specify file for client side public SSL certificate |
sslcertfile |
|
|
Specify file with trusted CA certificates |
sslcertpath |
|
|
Specify c_rehash-ed directory with trusted CA certificates. |
sslkey |
|
|
Specify file for client side private SSL key |
sslproto |
|
|
Force ssl protocol for connection |
folder |
-r |
|
Specify remote folder to query |
smtphost |
-S |
|
Specify smtp host(s) to forward to |
fetchdomains |
|
m |
Specify domains for which mail should be fetched |
smtpaddress |
-D |
|
Specify the domain to be put in RCPT TO lines |
smtpname |
|
|
Specify the user and domain to be put in RCPT TO lines |
antispam |
-Z |
|
Specify what SMTP returns are interpreted as spam-policy blocks |
mda |
-m |
|
Specify MDA for local delivery |
bsmtp |
-o |
|
Specify BSMTP batch file to append to |
preconnect |
|
|
Command to be executed before each connection |
postconnect |
|
|
Command to be executed after each connection |
keep |
-k |
|
Don't delete seen messages from server (for POP3, uidl is
recommended) |
flush |
-F |
|
Flush all seen messages before querying (DANGEROUS) |
limitflush |
|
|
Flush all oversized messages before querying |
fetchall |
-a |
|
Fetch all messages whether seen or not |
rewrite |
|
|
Rewrite destination addresses for reply (default) |
stripcr |
|
|
Strip carriage returns from ends of lines |
forcecr |
|
|
Force carriage returns at ends of lines |
pass8bits |
|
|
Force BODY=8BITMIME to ESMTP listener |
dropstatus |
|
|
Strip Status and X-Mozilla-Status lines out of incoming mail |
dropdelivered |
|
|
Strip Delivered-To lines out of incoming mail |
mimedecode |
|
|
Convert quoted-printable to 8-bit in MIME messages |
idle |
|
|
Idle waiting for new messages after each poll (IMAP only) |
no keep |
-K |
|
Delete seen messages from server (default) |
no flush |
|
|
Don't flush all seen messages before querying (default) |
no fetchall |
|
|
Retrieve only new messages (default) |
no rewrite |
|
|
Don't rewrite headers |
no stripcr |
|
|
Don't strip carriage returns (default) |
no forcecr |
|
|
Don't force carriage returns at EOL (default) |
no pass8bits |
|
|
Don't force BODY=8BITMIME to ESMTP listener (default) |
no dropstatus |
|
|
Don't drop Status headers (default) |
no dropdelivered |
|
|
Don't drop Delivered-To headers (default) |
no mimedecode |
|
|
Don't convert quoted-printable to 8-bit in MIME messages (default) |
no idle |
|
|
Don't idle waiting for new messages after each poll (IMAP only) |
limit |
-l |
|
Set message size limit |
warnings |
-w |
|
Set message size warning interval |
batchlimit |
-b |
|
Max # messages to forward in single connect |
fetchlimit |
-B |
|
Max # messages to fetch in single connect |
fetchsizelimit |
|
|
Max # message sizes to fetch in single transaction |
fastuidl |
|
|
Use binary search for first unseen message (POP3 only) |
expunge |
-e |
|
Perform an expunge on every #th message (IMAP and POP3 only) |
properties |
|
|
String value is ignored by fetchmail (may be used by extension
scripts) |
All user options must begin with a user description (user or username option)
and
follow all server descriptions and options.
In the .fetchmailrc file, the 'envelope' string argument may be preceded by a
whitespace-separated number. This number, if specified, is the number of such
headers to skip over (that is, an argument of 1 selects the second header of
the given type). This is sometime useful for ignoring bogus envelope headers
created by an ISP's local delivery agent or internal forwards (through mail
inspection systems, for instance).
Keywords Not Corresponding To Option Switches¶
The 'folder' and 'smtphost' options (unlike their command-line equivalents) can
take a space- or comma-separated list of names following them.
All options correspond to the obvious command-line arguments, except the
following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns',
'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect',
'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr',
'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus', 'dropdelivered/no
dropdelivered', 'mimedecode/no mimedecode', 'no idle', and 'no envelope'.
The 'via' option is for if you want to have more than one configuration pointing
at the same site. If it is present, the string argument will be taken as the
actual DNS name of the mailserver host to query. This will override the
argument of poll, which can then simply be a distinct label for the
configuration (e.g. what you would give on the command line to explicitly
query this host).
The 'interval' option (which takes a numeric argument) allows you to poll a
server less frequently than the basic poll interval. If you say 'interval N'
the server this option is attached to will only be queried every N poll
intervals.
Singledrop vs. Multidrop options¶
Please ensure you read the section titled
THE USE AND ABUSE OF MULTIDROP
MAILBOXES if you intend to use multidrop mode.
The 'is' or 'to' keywords associate the following local (client) name(s) (or
server-name to client-name mappings separated by =) with the mailserver user
name in the entry. If an is/to list has '*' as its last name, unrecognized
names are simply passed through. Note that until
fetchmail version
6.3.4 inclusively, these lists could only contain local parts of user names
(fetchmail would only look at the part before the @ sign).
fetchmail
versions 6.3.5 and newer support full addresses on the left hand side of these
mappings, and they take precedence over any 'localdomains', 'aka', 'via' or
similar mappings.
A single local name can be used to support redirecting your mail when your
username on the client machine is different from your name on the mailserver.
When there is only a single local name, mail is forwarded to that local
username regardless of the message's Received, To, Cc, and Bcc headers. In
this case,
fetchmail never does DNS lookups.
When there is more than one local name (or name mapping),
fetchmail looks
at the envelope header, if configured, and otherwise at the Received, To, Cc,
and Bcc headers of retrieved mail (this is 'multidrop mode'). It looks for
addresses with hostname parts that match your poll name or your 'via', 'aka'
or 'localdomains' options, and usually also for hostname parts which DNS tells
it are aliases of the mailserver. See the discussion of 'dns', 'checkalias',
'localdomains', and 'aka' for details on how matching addresses are handled.
If
fetchmail cannot match any mailserver usernames or localdomain
addresses, the mail will be bounced. Normally it will be bounced to the
sender, but if the 'bouncemail' global option is off, the mail will go to the
local postmaster instead. (see the 'postmaster' global option). See also BUGS.
The 'dns' option (normally on) controls the way addresses from multidrop
mailboxes are checked. On, it enables logic to check each host address that
does not match an 'aka' or 'localdomains' declaration by looking it up with
DNS. When a mailserver username is recognized attached to a matching hostname
part, its local mapping is added to the list of local recipients.
The 'checkalias' option (normally off) extends the lookups performed by the
'dns' keyword in multidrop mode, providing a way to cope with remote MTAs that
identify themselves using their canonical name, while they're polled using an
alias. When such a server is polled, checks to extract the envelope address
fail, and
fetchmail reverts to delivery using the To/Cc/Bcc headers
(See below 'Header vs. Envelope addresses'). Specifying this option instructs
fetchmail to retrieve all the IP addresses associated with both the
poll name and the name used by the remote MTA and to do a comparison of the IP
addresses. This comes in handy in situations where the remote server undergoes
frequent canonical name changes, that would otherwise require modifications to
the rcfile. 'checkalias' has no effect if 'no dns' is specified in the rcfile.
The 'aka' option is for use with multidrop mailboxes. It allows you to
pre-declare a list of DNS aliases for a server. This is an optimization hack
that allows you to trade space for speed. When
fetchmail, while
processing a multidrop mailbox, grovels through message headers looking for
names of the mailserver, pre-declaring common ones can save it from having to
do DNS lookups. Note: the names you give as arguments to 'aka' are matched as
suffixes -- if you specify (say) 'aka netaxs.com', this will match not just a
hostname netaxs.com, but any hostname that ends with '.netaxs.com'; such as
(say) pop3.netaxs.com and mail.netaxs.com.
The 'localdomains' option allows you to declare a list of domains which
fetchmail should consider local. When fetchmail is parsing address lines in
multidrop modes, and a trailing segment of a host name matches a declared
local domain, that address is passed through to the listener or MDA unaltered
(local-name mappings are
not applied).
If you are using 'localdomains', you may also need to specify 'no envelope',
which disables
fetchmail's normal attempt to deduce an envelope address
from the Received line or X-Envelope-To header or whatever header has been
previously set by 'envelope'. If you set 'no envelope' in the defaults entry
it is possible to undo that in individual entries by using 'envelope
<string>'. As a special case, 'envelope "Received"' restores
the default parsing of Received lines.
The
password option requires a string argument, which is the password to
be used with the entry's server.
The 'preconnect' keyword allows you to specify a shell command to be executed
just before each time
fetchmail establishes a mailserver connection.
This may be useful if you are attempting to set up secure POP connections with
the aid of
ssh(1). If the command returns a nonzero status, the poll of
that mailserver will be aborted.
Similarly, the 'postconnect' keyword similarly allows you to specify a shell
command to be executed just after each time a mailserver connection is taken
down.
The 'forcecr' option controls whether lines terminated by LF only are given CRLF
termination before forwarding. Strictly speaking RFC821 requires this, but few
MTAs enforce the requirement it so this option is normally off (only one such
MTA, qmail, is in significant use at time of writing).
The 'stripcr' option controls whether carriage returns are stripped out of
retrieved mail before it is forwarded. It is normally not necessary to set
this, because it defaults to 'on' (CR stripping enabled) when there is an MDA
declared but 'off' (CR stripping disabled) when forwarding is via SMTP. If
'stripcr' and 'forcecr' are both on, 'stripcr' will override.
The 'pass8bits' option exists to cope with Microsoft mail programs that stupidly
slap a "Content-Transfer-Encoding: 7bit" on everything. With this
option off (the default) and such a header present,
fetchmail declares
BODY=7BIT to an ESMTP-capable listener; this causes problems for messages
actually using 8-bit ISO or KOI-8 character sets, which will be garbled by
having the high bits of all characters stripped. If 'pass8bits' is on,
fetchmail is forced to declare BODY=8BITMIME to any ESMTP-capable
listener. If the listener is 8-bit-clean (as all the major ones now are) the
right thing will probably result.
The 'dropstatus' option controls whether nonempty Status and X-Mozilla-Status
lines are retained in fetched mail (the default) or discarded. Retaining them
allows your MUA to see what messages (if any) were marked seen on the server.
On the other hand, it can confuse some new-mail notifiers, which assume that
anything with a Status line in it has been seen. (Note: the empty Status lines
inserted by some buggy POP servers are unconditionally discarded.)
The 'dropdelivered' option controls whether Delivered-To headers will be kept in
fetched mail (the default) or discarded. These headers are added by Qmail and
Postfix mailservers in order to avoid mail loops but may get in your way if
you try to "mirror" a mailserver within the same domain. Use with
caution.
The 'mimedecode' option controls whether MIME messages using the
quoted-printable encoding are automatically converted into pure 8-bit data. If
you are delivering mail to an ESMTP-capable, 8-bit-clean listener (that
includes all of the major MTAs like sendmail), then this will automatically
convert quoted-printable message headers and data into 8-bit data, making it
easier to understand when reading mail. If your e-mail programs know how to
deal with MIME messages, then this option is not needed. The mimedecode option
is off by default, because doing RFC2047 conversion on headers throws away
character-set information and can lead to bad results if the encoding of the
headers differs from the body encoding.
The 'idle' option is intended to be used with IMAP servers supporting the
RFC2177 IDLE command extension, but does not strictly require it. If it is
enabled, and fetchmail detects that IDLE is supported, an IDLE will be issued
at the end of each poll. This will tell the IMAP server to hold the connection
open and notify the client when new mail is available. If IDLE is not
supported, fetchmail will simulate it by periodically issuing NOOP. If you
need to poll a link frequently, IDLE can save bandwidth by eliminating TCP/IP
connects and LOGIN/LOGOUT sequences. On the other hand, an IDLE connection
will eat almost all of your fetchmail's time, because it will never drop the
connection and allow other polls to occur unless the server times out the
IDLE. It also doesn't work with multiple folders; only the first folder will
ever be polled.
The 'properties' option is an extension mechanism. It takes a string argument,
which is ignored by fetchmail itself. The string argument may be used to store
configuration information for scripts which require it. In particular, the
output of '--configdump' option will make properties associated with a user
entry readily available to a Python script.
Miscellaneous Run Control Options¶
The words 'here' and 'there' have useful English-like significance. Normally
'user eric is esr' would mean that mail for the remote user 'eric' is to be
delivered to 'esr', but you can make this clearer by saying 'user eric there
is esr here', or reverse it by saying 'user esr here is eric there'
Legal protocol identifiers for use with the 'protocol' keyword are:
auto (or AUTO) (legacy, to be removed from future release)
pop2 (or POP2) (legacy, to be removed from future release)
pop3 (or POP3)
sdps (or SDPS)
imap (or IMAP)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are 'any', 'password', 'kerberos', 'kerberos_v4',
'kerberos_v5' and 'gssapi', 'cram-md5', 'otp', 'msn' (only for POP3), 'ntlm',
'ssh', 'external' (only IMAP). The 'password' type specifies authentication by
normal transmission of a password (the password may be plain text or subject
to protocol-specific encryption as in CRAM-MD5); 'kerberos' tells
fetchmail to try to get a Kerberos ticket at the start of each query
instead, and send an arbitrary string as the password; and 'gssapi' tells
fetchmail to use GSSAPI authentication. See the description of the 'auth'
keyword for more.
Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4
authentication. These defaults may be overridden by later options.
There are some global option statements: 'set logfile' followed by a string sets
the same global specified by --logfile. A command-line --logfile option will
override this. Note that --logfile is only effective if fetchmail detaches
itself from the terminal and the logfile already exists before fetchmail is
run, and it overrides --syslog in this case. Also, 'set daemon' sets the poll
interval as --daemon does. This can be overridden by a command-line --daemon
option; in particular --daemon 0 can be used to force foreground
operation. The 'set postmaster' statement sets the address to which multidrop
mail defaults if there are no local matches. Finally, 'set syslog' sends log
messages to
syslogd(8).
DEBUGGING FETCHMAIL¶
Fetchmail crashing¶
There are various ways in that fetchmail may "crash", i. e. stop
operation suddenly and unexpectedly. A "crash" usually refers to an
error condition that the software did not handle by itself. A well-known
failure mode is the "segmentation fault" or "signal 11" or
"SIGSEGV" or just "segfault" for short. These can be
caused by hardware or by software problems. Software-induced segfaults can
usually be reproduced easily and in the same place, whereas hardware-induced
segfaults can go away if the computer is rebooted, or powered off for a few
hours, and can happen in random locations even if you use the software the
same way.
For solving hardware-induced segfaults, find the faulty component and repair or
replace it. may help you with details.
For solving software-induced segfaults, the developers may need a "stack
backtrace".
Enabling fetchmail core dumps¶
By default, fetchmail suppresses core dumps as these might contain passwords and
other sensitive information. For debugging fetchmail crashes, obtaining a
"stack backtrace" from a core dump is often the quickest way to
solve the problem, and when posting your problem on a mailing list, the
developers may ask you for a "backtrace".
1. To get useful backtraces, fetchmail needs to be installed without getting
stripped of its compilation symbols. Unfortunately, most binary packages that
are installed are stripped, and core files from symbol-stripped programs are
worthless. So you may need to recompile fetchmail. On many systems, you can
type
file `which fetchmail`
to find out if fetchmail was symbol-stripped or not. If yours was unstripped,
fine, proceed, if it was stripped, you need to recompile the source code
first. You do not usually need to install fetchmail in order to debug it.
2. The shell environment that starts fetchmail needs to enable core dumps. The
key is the "maximum core (file) size" that can usually be configured
with a tool named "limit" or "ulimit". See the
documentation for your shell for details. In the popular bash shell,
"ulimit -Sc unlimited" will allow the core dump.
3. You need to tell fetchmail, too, to allow core dumps. To do this, run
fetchmail with the
-d0 -v options. It is often easier to also add
--nosyslog -N as well.
Finally, you need to reproduce the crash. You can just start fetchmail from the
directory where you compiled it by typing
./fetchmail, so the complete
command line will start with
./fetchmail -Nvd0 --nosyslog and
perhaps list your other options.
After the crash, run your debugger to obtain the core dump. The debugger will
often be GNU GDB, you can then type (adjust paths as necessary)
gdb
./fetchmail fetchmail.core and then, after GDB has started up and read all
its files, type
backtrace full, save the output (copy & paste will
do, the backtrace will be read by a human) and then type
quit to leave
gdb.
Note: on some systems, the core files have different names, they
might contain a number instead of the program name, or number and name, but it
will usually have "core" as part of their name.
INTERACTION WITH RFC 822¶
When trying to determine the originating address of a message, fetchmail looks
through headers in the following order:
Return-Path:
Resent-Sender: (ignored if it doesn't contain an @ or !)
Sender: (ignored if it doesn't contain an @ or !)
Resent-From:
From:
Reply-To:
Apparently-From:
The originating address is used for logging, and to set the MAIL FROM address
when forwarding to SMTP. This order is intended to cope gracefully with
receiving mailing list messages in multidrop mode. The intent is that if a
local address doesn't exist, the bounce message won't be returned blindly to
the author or to the list itself, but rather to the list manager (which is
less annoying).
In multidrop mode, destination headers are processed as follows: First,
fetchmail looks for the header specified by the 'envelope' option in order to
determine the local recipient address. If the mail is addressed to more than
one recipient, the Received line won't contain any information regarding
recipient addresses.
Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc: lines. If
they exist, they should contain the final recipients and have precedence over
their To:/Cc:/Bcc: counterparts. If the Resent-* lines don't exist, the To:,
Cc:, Bcc: and Apparently-To: lines are looked for. (The presence of a
Resent-To: is taken to imply that the person referred by the To: address has
already received the original copy of the mail.)
CONFIGURATION EXAMPLES¶
Note that although there are password declarations in a good many of the
examples below, this is mainly for illustrative purposes. We recommend
stashing account/password pairs in your $HOME/.netrc file, where they can be
used not just by fetchmail but by
ftp(1) and other programs.
The basic format is:
- poll SERVERNAME protocol PROTOCOL username NAME
password PASSWORD
Example:
-
poll pop.provider.net protocol pop3 username "jsmith" password "secret1"
Or, using some abbreviations:
-
poll pop.provider.net proto pop3 user "jsmith" password "secret1"
Multiple servers may be listed:
-
poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"
Here's the same version with more whitespace and some noise words:
-
poll pop.provider.net proto pop3
user "jsmith", with password secret1, is "jsmith" here;
poll other.provider.net proto pop2:
user "John.Smith", with password "My^Hat", is "John.Smith" here;
If you need to include whitespace in a parameter string or start the latter with
a number, enclose the string in double quotes. Thus:
-
poll mail.provider.net with proto pop3:
user "jsmith" there has password "4u but u can't krak this"
is jws here and wants mda "/bin/mail"
You may have an initial server description headed by the keyword 'defaults'
instead of 'poll' followed by a name. Such a record is interpreted as defaults
for all queries to use. It may be overwritten by individual server
descriptions. So, you could write:
-
defaults proto pop3
user "jsmith"
poll pop.provider.net
pass "secret1"
poll mail.provider.net
user "jjsmith" there has password "secret2"
It's possible to specify more than one user per server. The 'user' keyword leads
off a user description, and every user specification in a multi-user entry
must include it. Here's an example:
-
poll pop.provider.net proto pop3 port 3111
user "jsmith" with pass "secret1" is "smith" here
user jones with pass "secret2" is "jjones" here keep
This associates the local username 'smith' with the pop.provider.net username
'jsmith' and the local username 'jjones' with the pop.provider.net username
'jones'. Mail for 'jones' is kept on the server after download.
Here's what a simple retrieval configuration for a multidrop mailbox looks like:
-
poll pop.provider.net:
user maildrop with pass secret1 to golux 'hurkle'='happy' snark here
This says that the mailbox of account 'maildrop' on the server is a multidrop
box, and that messages in it should be parsed for the server user names
'golux', 'hurkle', and 'snark'. It further specifies that 'golux' and 'snark'
have the same name on the client as on the server, but mail for server user
'hurkle' should be delivered to client user 'happy'.
Note that
fetchmail, until version 6.3.4, did NOT allow full
user@domain specifications here, these would never match.
Fetchmail
6.3.5 and newer support user@domain specifications on the left-hand side of a
user mapping.
Here's an example of another kind of multidrop connection:
-
poll pop.provider.net localdomains loonytoons.org toons.org
envelope X-Envelope-To
user maildrop with pass secret1 to * here
This also says that the mailbox of account 'maildrop' on the server is a
multidrop box. It tells fetchmail that any address in the loonytoons.org or
toons.org domains (including sub-domain addresses like
'joe@daffy.loonytoons.org') should be passed through to the local SMTP
listener without modification. Be careful of mail loops if you do this!
Here's an example configuration using ssh and the plugin option. The queries are
made directly on the stdin and stdout of imapd via ssh. Note that in this
setup, IMAP authentication can be skipped.
-
poll mailhost.net with proto imap:
plugin "ssh %h /usr/sbin/imapd" auth ssh;
user esr is esr here
THE USE AND ABUSE OF MULTIDROP MAILBOXES¶
Use the multiple-local-recipients feature with caution -- it can bite. All
multidrop features are ineffective in ETRN and ODMR modes.
Also, note that in multidrop mode duplicate mails are suppressed. A piece of
mail is considered duplicate if it has the same message-ID as the message
immediately preceding and more than one addressee. Such runs of messages may
be generated when copies of a message addressed to multiple users are
delivered to a multidrop box.
The fundamental problem is that by having your mailserver toss several peoples'
mail in a single maildrop box, you may have thrown away potentially vital
information about who each piece of mail was actually addressed to (the
'envelope address', as opposed to the header addresses in the RFC822 To/Cc
headers - the Bcc is not available at the receiving end). This 'envelope
address' is the address you need in order to reroute mail properly.
Sometimes
fetchmail can deduce the envelope address. If the mailserver
MTA is
sendmail and the item of mail had just one recipient, the MTA
will have written a 'by/for' clause that gives the envelope addressee into its
Received header. But this doesn't work reliably for other MTAs, nor if there
is more than one recipient. By default,
fetchmail looks for envelope
addresses in these lines; you can restore this default with -E
"Received" or 'envelope Received'.
As a better alternative, some SMTP listeners and/or mail servers insert a
header in each message containing a copy of the envelope addresses. This
header (when it exists) is often 'X-Original-To', 'Delivered-To' or
'X-Envelope-To'. Fetchmail's assumption about this can be changed with the -E
or 'envelope' option. Note that writing an envelope header of this kind
exposes the names of recipients (including blind-copy recipients) to all
receivers of the messages, so the upstream must store one copy of the message
per recipient to avoid becoming a privacy problem.
Postfix, since version 2.0, writes an X-Original-To: header which contains a
copy of the envelope as it was received.
Qmail and Postfix generally write a 'Delivered-To' header upon delivering the
message to the mail spool and use it to avoid mail loops. Qmail virtual
domains however will prefix the user name with a string that normally matches
the user's domain. To remove this prefix you can use the -Q or 'qvirtual'
option.
Sometimes, unfortunately, neither of these methods works. That is the point when
you should contact your ISP and ask them to provide such an envelope header,
and you should not use multidrop in this situation. When they all fail,
fetchmail must fall back on the contents of To/Cc headers (Bcc headers are not
available - see below) to try to determine recipient addressees -- and these
are unreliable. In particular, mailing-list software often ships mail with
only the list broadcast address in the To header.
Note that a future version of fetchmail may remove To/Cc
parsing!
When
fetchmail cannot deduce a recipient address that is local, and the
intended recipient address was anyone other than fetchmail's invoking user,
mail will get lost. This is what makes the multidrop feature risky
without proper envelope information.
A related problem is that when you blind-copy a mail message, the Bcc
information is carried
only as envelope address (it's removed from the
headers by the sending mail server, so fetchmail can see it only if there is
an X-Envelope-To header). Thus, blind-copying to someone who gets mail over a
fetchmail multidrop link will fail unless the the mailserver host routinely
writes X-Envelope-To or an equivalent header into messages in your maildrop.
In conclusion, mailing lists and Bcc'd mail can only work if the
server you're fetching from
- (1)
- stores one copy of the message per recipient in your domain
and
- (2)
- records the envelope information in a special header
(X-Original-To, Delivered-To, X-Envelope-To).
Good Ways To Use Multidrop Mailboxes¶
Multiple local names can be used to administer a mailing list from the client
side of a
fetchmail collection. Suppose your name is 'esr', and you
want to both pick up your own mail and maintain a mailing list called (say)
"fetchmail-friends", and you want to keep the alias list on your
client machine.
On your server, you can alias 'fetchmail-friends' to 'esr'; then, in your
.fetchmailrc, declare 'to esr fetchmail-friends here'. Then, when mail
including 'fetchmail-friends' as a local address gets fetched, the list name
will be appended to the list of recipients your SMTP listener sees. Therefore
it will undergo alias expansion locally. Be sure to include 'esr' in the local
alias expansion of fetchmail-friends, or you'll never see mail sent only to
the list. Also be sure that your listener has the "me-too" option
set (sendmail's -oXm command-line option or OXm declaration) so your name
isn't removed from alias expansions in messages you send.
This trick is not without its problems, however. You'll begin to see this when a
message comes in that is addressed only to a mailing list you do
not
have declared as a local name. Each such message will feature an
'X-Fetchmail-Warning' header which is generated because fetchmail cannot find
a valid local name in the recipient addresses. Such messages default (as was
described above) to being sent to the local user running
fetchmail, but
the program has no way to know that that's actually the right thing.
Bad Ways To Abuse Multidrop Mailboxes¶
Multidrop mailboxes and
fetchmail serving multiple users in daemon mode
do not mix. The problem, again, is mail from mailing lists, which typically
does not have an individual recipient address on it. Unless
fetchmail
can deduce an envelope address, such mail will only go to the account running
fetchmail (probably root). Also, blind-copied users are very likely never to
see their mail at all.
If you're tempted to use
fetchmail to retrieve mail for multiple users
from a single mail drop via POP or IMAP, think again (and reread the section
on header and envelope addresses above). It would be smarter to just let the
mail sit in the mailserver's queue and use fetchmail's ETRN or ODMR modes to
trigger SMTP sends periodically (of course, this means you have to poll more
frequently than the mailserver's expiry period). If you can't arrange this,
try setting up a UUCP feed.
If you absolutely
must use multidrop for this purpose, make sure your
mailserver writes an envelope-address header that fetchmail can see. Otherwise
you
will lose mail and it
will come back to haunt you.
Speeding Up Multidrop Checking¶
Normally, when multiple users are declared
fetchmail extracts recipient
addresses as described above and checks each host part with DNS to see if it's
an alias of the mailserver. If so, the name mappings described in the "to
... here" declaration are done and the mail locally delivered.
This is a convenient but also slow method. To speed it up, pre-declare
mailserver aliases with 'aka'; these are checked before DNS lookups are done.
If you're certain your aka list contains
all DNS aliases of the
mailserver (and all MX names pointing at it - note this may change in a future
version) you can declare 'no dns' to suppress DNS lookups entirely and
only match against the aka list.
SOCKS¶
Support for socks4/5 is a
compile time configuration option. Once
compiled in, fetchmail will always use the socks libraries and configuration
on your system, there are no run-time switches in fetchmail - but you can
still configure SOCKS: you can specify which SOCKS configuration file is used
in the
SOCKS_CONF environment variable.
For instance, if you wanted to bypass the SOCKS proxy altogether and have
fetchmail connect directly, you could just pass SOCKS_CONF=/dev/null in the
environment, for example (add your usual command line options - if any - to
the end of this line):
env SOCKS_CONF=/dev/null fetchmail
EXIT CODES¶
To facilitate the use of
fetchmail in shell scripts, an
exit status code is returned to give an indication of what occurred
during a given connection.
The exit codes returned by
fetchmail are as follows:
- 0
- One or more messages were successfully retrieved (or, if the -c option was
selected, were found waiting but not retrieved).
- 1
- There was no mail awaiting retrieval. (There may have been old mail still
on the server but not selected for retrieval.) If you do not want "no
mail" to be an error condition (for instance, for cron jobs), use a
POSIX-compliant shell and add
|| [ $? -eq 1 ]
to the end of the fetchmail command line, note that this leaves 0 untouched,
maps 1 to 0, and maps all other codes to 1. See also item #C8 in the
FAQ.
- 2
- An error was encountered when attempting to open a socket to retrieve
mail. If you don't know what a socket is, don't worry about it -- just
treat this as an 'unrecoverable error'. This error can also be because a
protocol fetchmail wants to use is not listed in /etc/services.
- 3
- The user authentication step failed. This usually means that a bad
user-id, password, or APOP id was specified. Or it may mean that you tried
to run fetchmail under circumstances where it did not have standard input
attached to a terminal and could not prompt for a missing password.
- 4
- Some sort of fatal protocol error was detected.
- 5
- There was a syntax error in the arguments to fetchmail, or a pre-
or post-connect command failed.
- 6
- The run control file had bad permissions.
- 7
- There was an error condition reported by the server. Can also fire if
fetchmail timed out while waiting for the server.
- 8
- Client-side exclusion error. This means fetchmail either found
another copy of itself already running, or failed in such a way that it
isn't sure whether another copy is running.
- 9
- The user authentication step failed because the server responded
"lock busy". Try again after a brief pause! This error is not
implemented for all protocols, nor for all servers. If not implemented for
your server, "3" will be returned instead, see above. May be
returned when talking to qpopper or other servers that can respond with
"lock busy" or some similar text containing the word
"lock".
- 10
- The fetchmail run failed while trying to do an SMTP port open or
transaction.
- 11
- Fatal DNS error. Fetchmail encountered an error while performing a DNS
lookup at startup and could not proceed.
- 12
- BSMTP batch file could not be opened.
- 13
- Poll terminated by a fetch limit (see the --fetchlimit option).
- 14
- Server busy indication.
- 23
- Internal error. You should see a message on standard error with
details.
- 24 - 26, 28, 29
- These are internal codes and should not appear externally.
When
fetchmail queries more than one host, return status is 0 if
any query successfully retrieved mail. Otherwise the returned error
status is that of the last host queried.
FILES¶
- ~/.fetchmailrc
- default run control file
- ~/.fetchids
- default location of file recording last message UIDs seen per host.
- ~/.fetchmail.pid
- lock file to help prevent concurrent runs (non-root mode).
- ~/.netrc
- your FTP run control file, which (if present) will be searched for
passwords as a last resort before prompting for one interactively.
- /var/run/fetchmail.pid
- lock file to help prevent concurrent runs (root mode, Linux systems).
- /etc/fetchmail.pid
- lock file to help prevent concurrent runs (root mode, systems without
/var/run).
ENVIRONMENT¶
- FETCHMAILHOME
- If this environment variable is set to a valid and existing directory
name, fetchmail will read $FETCHMAILHOME/fetchmailrc (the dot is missing
in this case), $FETCHMAILHOME/.fetchids and $FETCHMAILHOME/.fetchmail.pid
rather than from the user's home directory. The .netrc file is always
looked for in the the invoking user's home directory regardless of
FETCHMAILHOME's setting.
- FETCHMAILUSER
- If this environment variable is set, it is used as the name of the calling
user (default local name) for purposes such as mailing error
notifications. Otherwise, if either the LOGNAME or USER variable is
correctly set (e.g. the corresponding UID matches the session user ID)
then that name is used as the default local name. Otherwise
getpwuid(3) must be able to retrieve a password entry for the
session ID (this elaborate logic is designed to handle the case of
multiple names per userid gracefully).
- FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE
- (since v6.3.22): If this environment variable is set and not empty,
fetchmail will disable a countermeasure against an SSL CBC IV attack (by
setting SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS). This is a security risk, but
may be necessary for connecting to certain non-standards-conforming
servers. See fetchmail's NEWS file and fetchmail-SA-2012-01.txt for
details. Earlier fetchmail versions (v6.3.21 and older) used to disable
this countermeasure, but v6.3.22 no longer does that as a safety
precaution.
- FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS
- (since v6.3.17): If this environment variable is set and not empty,
fetchmail will always load the default X.509 trusted certificate locations
for SSL/TLS CA certificates, even if --sslcertfile and
--sslcertpath are given. The latter locations take precedence over
the system default locations. This is useful in case there are broken
certificates in the system directories and the user has no administrator
privileges to remedy the problem.
- HOME_ETC
- If the HOME_ETC variable is set, fetchmail will read
$HOME_ETC/.fetchmailrc instead of ~/.fetchmailrc.
If HOME_ETC and FETCHMAILHOME are both set, HOME_ETC will be ignored.
- SOCKS_CONF
- (only if SOCKS support is compiled in) this variable is used by the socks
library to find out which configuration file it should read. Set this to
/dev/null to bypass the SOCKS proxy.
SIGNALS¶
If a
fetchmail daemon is running as root, SIGUSR1 wakes it up from its
sleep phase and forces a poll of all non-skipped servers. For compatibility
reasons, SIGHUP can also be used in 6.3.X but may not be available in future
fetchmail versions.
If
fetchmail is running in daemon mode as non-root, use SIGUSR1 to wake
it (this is so SIGHUP due to logout can retain the default action of killing
it).
Running
fetchmail in foreground while a background fetchmail is running
will do whichever of these is appropriate to wake it up.
BUGS, LIMITATIONS, AND KNOWN PROBLEMS¶
Please check the
NEWS file that shipped with fetchmail for more known
bugs than those listed here.
Fetchmail cannot handle user names that contain blanks after a "@"
character, for instance "demonstr@ti on". These are rather uncommon
and only hurt when using UID-based --keep setups, so the 6.3.X versions of
fetchmail won't be fixed.
Fetchmail cannot handle configurations where you have multiple accounts that use
the same server name and the same login. Any user@server combination must be
unique.
The assumptions that the DNS and in particular the checkalias options make are
not often sustainable. For instance, it has become uncommon for an MX server
to be a POP3 or IMAP server at the same time. Therefore the MX lookups may go
away in a future release.
The mda and plugin options interact badly. In order to collect error status from
the MDA, fetchmail has to change its normal signal handling so that dead
plugin processes don't get reaped until the end of the poll cycle. This can
cause resource starvation if too many zombies accumulate. So either don't
deliver to a MDA using plugins or risk being overrun by an army of undead.
The --interface option does not support IPv6 and it is doubtful if it ever will,
since there is no portable way to query interface IPv6 addresses.
The RFC822 address parser used in multidrop mode chokes on some @-addresses that
are technically legal but bizarre. Strange uses of quoting and embedded
comments are likely to confuse it.
In a message with multiple envelope headers, only the last one processed will be
visible to fetchmail.
Use of some of these protocols requires that the program send unencrypted
passwords over the TCP/IP connection to the mailserver. This creates a risk
that name/password pairs might be snaffled with a packet sniffer or more
sophisticated monitoring software. Under Linux and FreeBSD, the --interface
option can be used to restrict polling to availability of a specific interface
device with a specific local or remote IP address, but snooping is still
possible if (a) either host has a network device that can be opened in
promiscuous mode, or (b) the intervening network link can be tapped. We
recommend the use of
ssh(1) tunnelling to not only shroud your
passwords but encrypt the entire conversation.
Use of the %F or %T escapes in an mda option could open a security hole, because
they pass text manipulable by an attacker to a shell command. Potential shell
characters are replaced by '_' before execution. The hole is further reduced
by the fact that fetchmail temporarily discards any suid privileges it may
have while running the MDA. For maximum safety, however, don't use an mda
command containing %F or %T when fetchmail is run from the root account
itself.
Fetchmail's method of sending bounces due to errors or spam-blocking and spam
bounces requires that port 25 of localhost be available for sending mail via
SMTP.
If you modify
~/.fetchmailrc while a background instance is running and
break the syntax, the background instance will die silently. Unfortunately, it
can't die noisily because we don't yet know whether syslog should be enabled.
On some systems, fetchmail dies quietly even if there is no syntax error; this
seems to have something to do with buggy terminal ioctl code in the kernel.
The -f - option (reading a configuration from stdin) is incompatible with
the plugin option.
The 'principal' option only handles Kerberos IV, not V.
Interactively entered passwords are truncated after 63 characters. If you really
need to use a longer password, you will have to use a configuration file.
A backslash as the last character of a configuration file will be flagged as a
syntax error rather than ignored.
The BSMTP error handling is virtually nonexistent and may leave broken messages
behind.
Send comments, bug reports, gripes, and the like to the
An is available at the fetchmail home page, it should also accompany your
installation.
AUTHOR¶
Fetchmail is currently maintained by Matthias Andree and Rob Funk with major
assistance from Sunil Shetye (for code) and Rob MacGregor (for the mailing
lists).
Most of the code is from . Too many other people to name here have contributed
code and patches.
This program is descended from and replaces
popclient, by ; the internals
have become quite different, but some of its interface design is directly
traceable to that ancestral program.
This manual page has been improved by Matthias Andree, R. Hannes Beinert,
and Héctor García.
SEE ALSO¶
README,
README.SSL,
README.SSL-SERVER,
mutt(1),
elm(1),
mail(1),
sendmail(8),
popd(8),
imapd(8),
netrc(5).
APPLICABLE STANDARDS¶
Note that this list is just a collection of references and not a statement as to
the actual protocol conformance or requirements in fetchmail.
- SMTP/ESMTP:
- RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985, RFC
2554.
- mail:
- RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.
- POP2:
- RFC 937
- POP3:
- RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC 1957, RFC
2195, RFC 2449.
- APOP:
- RFC 1939.
- RPOP:
- RFC 1081, RFC 1225.
- IMAP2/IMAP2BIS:
- RFC 1176, RFC 1732.
- IMAP4/IMAP4rev1:
- RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177, RFC
2683.
- ETRN:
- RFC 1985.
- ODMR/ATRN:
- RFC 2645.
- OTP:
- RFC 1938.
- LMTP:
- RFC 2033.
- GSSAPI:
- RFC 1508, RFC 1734,
- TLS:
- RFC 2595.