Msg#: 4050657 posted 9:23 pm on Dec 31, 2009 (gmt 0)
If you have a problem, *save* your log files, don't delete them! Or at least download and save part of the log files...
Check your FormMail (or similar script) to be sure that it is up-to-date and secure. Make sure that it does not accept newlines or any special characters in any of the 'address' headers such as 'To', 'From', 'CC', 'BCC', 'Reply-to' or 'Subject'. If it does, then it will be quite easy to send spam from your server using simple injection tricks.
If your server is commercially-hosted, ask your host for help. If they can't help, then you need a new host.