In fact, most bloated mail gets killed at my server without me knowing its fate. I set that up and it's served me well because now another massive worm attack is sweeping the Internet. The WELL's email server is killing all mail over 150K in size until the storm of virus-laden mail subsides. It's probably good if you invoke this rule as well. You could try to screen all arriving mail as it arrives, but most mail systems bog down when trying to cope with an all-out virus flood. Just yesterday, I received two e-mails sent to me by separate people during the second week of August. They were fuming at the end of August because they didn't believe I hadn't seen their original e-mail.
For the record, the current worm poses as a Mircosoft security patch, and looks quite authentic. If you use a PC and get an email from Microsoft instructing you to install the "September, 2003, Cumulative Patch" update, you are mad if you open the attachment. This is the latest worm to target Microsoft operating systems. It poses as a security update sent from a forged email address and looks very, very similar to legitimate security updates. You can see a screenshot of the email message at Arstechnica along with good information about the Swen.A@mm worm.
Bernie Goldbach's main mail is at The Well.