Having a scanner/filter installed on your mail servers is a very good thing, as well. We were able to set a block in just a few minutes against the majority of the SoBig.E items while we got the anti-virus updates out to our network workstations and servers. I can remove the block, now, or fine tune it to be more effective.

Odd how these variations on a theme get you to looking at network protection from different angles every time a new worm shows up.