Scan Outgoing Mail
What would be the best way to scan outgoing mail to check if it is spam and block it?
Centos 5.5 Perfect Server, postfix, spamassassin, clamav, ispConfig 2.
The incoming mail is well scanned, and using greylisting, spamassassin, clamav and so on has reduced incoming spam quite well. The problem is that a few times one or another of our email clients have sent spam, and a few times weak PHP programming has allowed spammers to compromise our server by writing PHP files to 777 directories and POSTING to them. In those cases, I think sendmail is handling the mail sending.
What I would like to do is scan the outgoing mail with spamassassin and route emails with high scores to a directory where we can monitor them. I want to stop the emails from being sent.
What would work best? Any ideas?