Problem with Spammer or Hacker?

Hello,

I have one of two sites running with WordPress. The one with the issue runs a fully of WordPress, including a forum plug-in.

The problem I am having is that it seems a hacker or malicious code has been implemented to use my email account to send Spam. I say this because it seems that every time a comment is posted, I get instantly get plenty of Undeliverable emails. It doesn’t happen as frequently as when there is actually some kind of site activity, primarily in the area of comments.

Wondering if anyone knows how to troubleshoot this issue? I’d hate to end up on some blacklist as a result!

Thanks,

–mike