MIMEHeader - perform regexp tests against MIME headers
loadplugin Mail::SpamAssassin::Plugin::MIMEHeader mimeheader NAME_OF_RULE Content-Id =~ /foo/
This plugin allows regexp rules to be written against MIME headers in the message.
Specify a rule. NAME_OF_RULE is the name of the rule to be used,
Header-Name is the name of the MIME header to check, and
/pattern/modifiers is the Perl regular expression to match against this.
Note that in a message of multiple parts, each header will be checked against the pattern separately. In other words, if multiple parts have a 'Content-Type' header, each header's value will be tested individually as a separate string.
Header names are considered case-insensitive.
The header values are normally cleaned up a little; for example, whitespace
around the newline character in "folded" headers will be replaced with a single
space. Append :raw to the header name to retrieve the raw, undecoded value,
including pristine whitespace, instead.