Well, let me just say that procmail is an awful, awful program. However, my system won't let me use anything nice (like say, a perl script using Mail::Procmail) to filter mail. After about a week, I've finally worked up a set of rules that seem to catch 95% or more of all my spam messages.

As part of my ruleset, I check the 'from:' header of the message against my pine .addressbook file, and if the user is known they go into the inbox -- essentially a whitelist scheme. I wrote a little perl script to check the values.

#!/usr/local/bin/perl
use strict;
exit 1 unless (my $mail_from = <>);
exit 1 unless open (AD,'/home/ajdelore/.addressbook');
while (<AD>) {
  my $addr = (split /\t/)[2];
  $addr =~ s/\s+//g;
  exit 0 if $mail_from =~ /$addr/i;
}
exit 1;
[download]

The rule I use in procmail is:

:0
* ^From:\/.*
{
  :0:
  * ? echo $MATCH | /home/ajdelore/bin/check_addr.pl
  ${DEFAULT}
}
[download]

</ajdelore>