Note: written before parent node was updated.

Good idea, but far less than enough hubris. You can replace the entire repetitive beginning of the script by just a few lines:

sub make_rx_from {
    open my $fh, "<", shift or warn("Can't open fromgood $!\n"), retur
+n;
    chomp(my @line = <$fh>);
    return map qr/$_/, @line;
}

my @togood       = make_rx_from "togood";
my @receivedgood = make_rx_from "receivedgood";
my @badcontent   = make_rx_from "contentbad";
my @maillists    = make_rx_from "maillist";
my @badwords     = make_rx_from "badwords";
my @frombad      = make_rx_from "frombad";
my @fromgood     = make_rx_from "fromgood";

[download]
But that's still far from ideal. Look at your code's main loop: you are examining a specific header, testing it against a whitelist and a blacklist, flagging accordingly. The same pattern every time. That can be factored out along these lines: 
HEADER: foreach my $line (@$messref) {
    # detects first blank line go do body check of first 10 body lines
    last if $line =~ /^\s*$/;

    my ($header) = grep $line =~ /^$_:/i, keys %test_for;
    next unless $header;

    for my $test (qw(ok bad)) {
        my @match = grep $line =~ $_, @{ $test_for{$header}{$test} };
        next if not @match;
        $flag = $test; 
        print "Message $test - header $header matched: @match\n";
        last HEADER;
    }
}

[download]
You could also check the message size prior to any other tests for efficiency. I'll post the complete code as I refactored it in a separate node, for easier downloading.

Makeshifts last the longest.

In reply to Re: dialup spam removal with Net::POP3 (program repair shop) by Aristotle
in thread dialup spam removal with Net::POP3 by zentara

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.