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.IX Title "Mail::SpamAssassin::Plugin::MIMEEval 3pm"
.TH Mail::SpamAssassin::Plugin::MIMEEval 3pm "2021-03-26" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Mail::SpamAssassin::Plugin::MIMEEval \- perform various tests against MIME structure and body
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  loadplugin    Mail::SpamAssassin::Plugin::MIMEEval
\&
\&  body NAME_OF_RULE  eval:check_for_mime
\&  body NAME_OF_RULE  eval:check_for_mime_html
\&  body NAME_OF_RULE  eval:check_for_mime_html_only
\&  body NAME_OF_RULE  eval:check_mime_multipart_ratio
\&  body NAME_OF_RULE  eval:check_msg_parse_flags
\&  body NAME_OF_RULE  eval:check_for_ascii_text_illegal
\&  body NAME_OF_RULE  eval:check_abundant_unicode_ratio
\&  body NAME_OF_RULE  eval:check_for_faraway_charset
\&  body NAME_OF_RULE  eval:check_for_uppercase
\&  body NAME_OF_RULE  eval:check_ma_non_text
\&  body NAME_OF_RULE  eval:check_base64_length
\&  body NAME_OF_RULE  eval:check_qp_ratio
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Perform various tests against \s-1MIME\s0 structure and body.
.IP "has_check_for_ascii_text_illegal" 4
.IX Item "has_check_for_ascii_text_illegal"
Adds capability check for \*(L"if \fBcan()\fR\*(R" for check_for_ascii_text_illegal
.IP "check_for_ascii_text_illegal" 4
.IX Item "check_for_ascii_text_illegal"
If a \s-1MIME\s0 part claims to be text/plain or text/plain;charset=us\-ascii and the Content-Transfer-Encoding is 7bit (either explicitly or by default), then we should enforce the actual text being only \s-1TAB, NL, SPACE\s0 through \s-1TILDE,\s0 i.e. all 7bit characters excluding NO-WS-CTL (per \s-1RFC\-2822\s0).
.Sp
All mainstream \s-1MTA\s0's get this right.
.IP "has_check_abundant_unicode_ratio" 4
.IX Item "has_check_abundant_unicode_ratio"
Adds capability check for \*(L"if \fBcan()\fR\*(R" for check_abundant_unicode_ratio
.IP "check_abundant_unicode_ratio" 4
.IX Item "check_abundant_unicode_ratio"
A \s-1MIME\s0 part claiming to be text/plain and containing Unicode characters must be encoded as quoted-printable or base64, or use \s-1UTF\s0 data coding (typically with 8bit encoding).  Any message in 7bit or 8bit encoding containing (\s-1HTML\s0) Unicode entities will not render them as Unicode, but literally.
.Sp
Thus a few such sequences might occur on a mailing list of developers discussing such characters, but a message with a high density of such characters is likely spam.
.IP "check_for_mime" 4
.IX Item "check_for_mime"
Check for various \s-1MIME\s0 properties.
.Sp
Use in rules such as:
.Sp
.Vb 2
\&  rawbody MIME_BASE64      eval:check_for_mime(\*(Aqmime_base64_count\*(Aq)
\&  describe MIME_BASE64     Includes a base64 attachment
\&
\&  mime_base64_count
\&  mime_base64_encoded_text
\&  mime_body_html_count
\&  mime_body_text_count
\&  mime_faraway_charset
\&  mime_missing_boundary
\&  mime_multipart_alternative
\&  mime_multipart_ratio
\&  mime_qp_count
\&  mime_qp_long_line
\&  mime_qp_ratio
\&  mime_ascii_text_illegal
\&  mime_text_unicode_ratio
.Ve
.IP "check_for_mime_html_only" 4
.IX Item "check_for_mime_html_only"
Check for messages containing only text/html body parts
.IP "has_check_qp_ratio" 4
.IX Item "has_check_qp_ratio"
Adds capability check for \*(L"if \fBcan()\fR\*(R" for check_qp_ratio
.IP "check_qp_ratio" 4
.IX Item "check_qp_ratio"
Takes a min ratio to use in eval to see if there is an spamminess to the ratio of 
quoted printable to total bytes in an email.