In the process of moving servers I’ve had to get used to the provider imposed Postini message filtering system. Initially I wasn’t really happy about the imposition it seemed to place on the way I like to use email, i.e. lots of “catch all” addresses.

After puttering around with the system for a little over a day I can honestly say that once I figured out how it worked, I ended up liking it. It’s really made a dent in the amount of daily spam that I’m receiving even while retaining a “catch-all” capability. What I did was the following:

  1. Merged most of the domains that I manage into a common domain from Postini’s point of view so that mail coming from those domains is treated by a single set of Postini rules.
  2. Created Postini based email addresses that matched the specific email addresses that were serving as “catch-all” mail boxes at the various domains.
  3. For each mail box, established a list of Postini “user” aliases that I wanted to run the Postini spam filtering against. Addresses not matching the mail box name or the aliases go through the Postini system without filtering.
  4. From the spam emails that were avoiding the Postini filter from step #3, I pulled out the most commonly used addresses and through my ISP established email forwarding rules that directed those addresses to a non-existent account causing emails using that address to bounce. In some specific cases I added the address as an approved “user” alias at Postini.
  5. Kept repeating step 4 until the level of spam fell to near zero

Sounds like a lot of work, but in reality it wasn’t. The hardest part was wrapping my head around the way Postini handles catch-all addressing in the absence of a specific option. I had to just “trial and error” it until I figured it out. Once I understood the “rules” I quickly figured out how to leverage the Postini configuration and my ISP’s email forwarding rules to work in conjunction to achieve a better email filtering system. In essence I’m using the stuff that gets through Postini as a feedback loop to the email forwarding system. Right now step 4 is a manual process but I could easily make that programmatic.

At any rate, by the end of day 2 my email has gone from near 1000 pieces of spam per day down to a managable 100 or so and dropping every time I get new spam. Not bad for a few hours invested in figuring out the constraints and learning to work effectively within them.

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