If your mail server sends it, you're contributing to a growing problem.
I don't know what's worse:
- All the blocked messages from the poorly designed Barracuda anti-spam filtering devices out there in the wild. (Accept-then-reject spam filtering is so 1998.)
- All the random "Confirm your YahooGroups signup request" emails. (Allowing email signup requests to be originated via email is so 1998.)
- All the rest of it I get (bounces from spams forging my domains, etc.).