[Mimedefang] re: powerful anti-spam rule :-)

[David F. Skoll]

On Thu, 7 Nov 2002, Douglas J Hunley wrote:

> any chance you could pseudo-code this up David? I'm drawing a blank here. I
> know it's been on this list before..

OK, here we go, Writing Untested Perl Code While Replying To Mail (tm):

# Only allow from certain domains if relay hostname ends in same domain
sub filter_sender {
    my($sender, $hostip, $hostname, $helo) = @_;
    my($i1, $i2);

    # Regularize sender to lower-case, no <> signs
    $sender = lc($sender);
    $sender =~ tr/<>//d;
    foreach $domain qw(aol.com hotmail.com earthlink.net yahoo.com) {
        $i1 = rindex($sender, $domain);
        $i2 = rindex($hostname, $domain);
        if ($i1 >= 0 and $i1 == length($sender) - length($domain)) {
            if (length($hostname) < length($domain) or
                $i2 != length($hostname) - length($domain)) {
                return(0, "Mail from $domain not permitted from relay $hostip");
            }
        }
    }
    return (1, "OK");
}

Regards,

David.