[CentOS] find out which website is used for sending email?

Tue Oct 27 06:50:38 UTC 2009
Peter Peltonen <peter.peltonen at gmail.com>

I got a report that my CentOS 5.4 is used for sending spam.

>From sendmail maillog I can see that apache has been sending a lot of
email to suspicious addresses.

Probably one of the many Apache virtual hosts I have is used for
sending spam. But how to find out which one?

Regards,
Peter