[pmmail-list] Filter for SPAM

Tue, 19 Mar 2002 14:41:30 -0500 (EST)

I think one of the most critical factors in building effective spam
filters is their placement in the cascading sequence of different
filters set up in PMMail.  For instance, I first have a series of
filters that move all the emails I expect to receive from newsgroups,
known vendors, newsletters, business contacts, etc. into appropriate
folders.  It is only after all those emails have been safely moved to
folders that the remaining messages are filtered through my junk
filters.  The first junk filter looks for any header that does not
contain my email address or the address of other trusted senders and it
moves those messages into a Junk folder.  The second junk filter looks
for specific strings in messages that generally show up in spam and
moves those messages to the Junk folder.  Here's that filter:

On the average day I receive a couple hundred emails, approximately 50
of which are spam.  Together, the filters I use redirect 99%+ of the
spam emails to the Junk folder.  All the other emails that are not
redirected by any of my filters end up in my Inbox where they belong.

Keep in mind that while it may be tempting to send messages caught by
your junk filters directly to the Trash folder, I'd advise you against
it.  By sending those messages to the Junk folder instead, you have a
chance to review them to make sure that a legitimate email hasn't
gotten snagged by mistake.  If you find a message in there that belongs
somewhere else, you know you need to modify one or more of your filters
to keep it from happening again.  

Also, try to resist the temptation to make your junk filters too broad.
 For instance, redirecting all email from Hotmail to the junk folder
may seem like a good idea, but chances are messages will end up in
there that are not junk.  I've also seen junk filters that dump
everything coming in from entire countries such as Korea (kr) into the
junk bin, but once again you that could come back to bite you. 
Filtering spam is a dynamic process and by monitoring the contents of
your Junk folder as well as any spam that isn't caught, you can keep
your junk filters tuned for maximum efficacy.

Ralph Cohen

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