NAME

       Mail::SpamAssassin::Plugin::MIMEEval - perform various tests against MIME structure and
       body

SYNOPSIS

         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

DESCRIPTION

       Perform various tests against MIME structure and body.

       has_check_for_ascii_text_illegal
           Adds capability check for "if can()" for check_for_ascii_text_illegal

       check_for_ascii_text_illegal
           If a MIME 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 TAB, NL, SPACE through TILDE, i.e. all 7bit characters
           excluding NO-WS-CTL (per RFC-2822).

           All mainstream MTA's get this right.

       has_check_abundant_unicode_ratio
           Adds capability check for "if can()" for check_abundant_unicode_ratio

       check_abundant_unicode_ratio
           A MIME part claiming to be text/plain and containing Unicode characters must be
           encoded as quoted-printable or base64, or use UTF data coding (typically with 8bit
           encoding).  Any message in 7bit or 8bit encoding containing (HTML) Unicode entities
           will not render them as Unicode, but literally.

           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.

       check_for_mime
           Check for various MIME properties.

           Use in rules such as:

             rawbody MIME_BASE64      eval:check_for_mime('mime_base64_count')
             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

       check_for_mime_html_only
           Check for messages containing only text/html body parts

       has_check_qp_ratio
           Adds capability check for "if can()" for check_qp_ratio

       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.