Well, our cPanel2 server went into overload this morning.  We found out that one of our users had an exploited script where an end user was exploiting it to post links to websites (link spam). The Guestbook was 90 megs.. and the coding for the guestbook was very poor, so each request loaded 90 megs into memory and it would just kill the server with each rapid request.

So, we got that issue resolved and disabled the scripts for that user.  The server has already processed all the mail, so things should be back to normal. Please let us know if you still are having problems.