Safe spam filtering
I use Spam Assassin for some addresses these days, and I’ve done some investigating on how to safely filter spam.
What I came up with, was that with the addresses I have going through the test server these days, I could probably discard mail with 14 or more stars, and not have a single positive.
Each address and domain is different in regard to the type of spam and “legitimate” mail it takes in, so don’t take this as gospel without a testing period. On one domain I have, I got lots of forwards and people who made their own mailing lists. When you’ve got a typical forward, to a long list of e-mail addresses, with a Yahoo address sent from a mail client (not from their web interface), that mail gets a lot of punitive stars by Spam Assassin. Enough to boost it over the tagging threshold of 5 I had at first (I boosted it to 6 because I’m probably not the only one who have clueless friends…).
But for now I don’t discard, and sorting through 99 mails a day sorting the tagged spam for possible false positives was driving me up the wall. So, how could I cut down on the amount of sorting I have to do, and still be able to sort those that may potentially be false positives by hand?
Well, if you’ve got Pegasus Mail, that’s not a problem, because you can sort by number of stars. Here’s my filtering rule:
*X-Spam-Level: [*][*][*][*][*][*][*][*][*][*][*][*][*][*]*
And I add that one by opening the filtering rules, clicking Add Rule, and choosing Expression. Then enter that phrase (double check that your Spam Assassin actually uses the header tagging that way, and possibly change the line).
Then go to Action, choose Move and choose the folder you want them moved to by clicking on Set.
How would we do this with other mail programs? Is it possible to filter by number of stars (14 or more, for instance) in Outlook Express, Outlook or Thunderbird?
It took me some researching to get the rule right in Pegasus, because * is a wildcard character, and had to be escaped to get it right.
December 8th, 2005 at 3:06 pm
Thunderbird allows you to filter on custom header fields. I’ve done it before on spamassassin-marked mail, and it works well. In this instance, just add the field ‘X-Spam-Level’ and have it match a number of stars equal to the lowest threshold you want to match. I’m not sure about outlook express/outlook, but I have my doubts.