Is it possible to create a mail alert if a domain is sending (too much) mail? I've got a Joomla-site which was hacked due too updating in this case (and not removing the update files which left the site vulnerable for attacks). The domain was sending a lot of Spam, and I was not notified in any way. Because of this I would really like to be notified if some site was sending more mail then a certain threshold, for example 100 e-mails a minute. Could someone shed a light on this subject? Maybe it's doable through Postfix, but I don't know if and how.
In such a case you will normally see an increase of message in the mailqueue (postqueue -p) command. It should be possible to monitor the mailqueue with Nagios and then get an Alert on your mobile phone by using one of the Nagios apps.
