Question : Restrict Outgoing Spam (Icewarp Merak Mail Server)

Dear Experts,

I am using Icewarp's Merak Mail Server to host emails for approximately 2000 accounts.  And recently we have found out that some emails account were sending out hundreds of spam mail.  I am still investigating as to whether the users were purposely doing spam sending, or if our server were compromised by hackers and sending out them.  

In the mean while, these out-going spam drains all the resources out of our emails server, the server response very slowly, and legitimate emails gets queue up so far behind, and they don't get delivered after 1-2 days.

I am desperately trying to find a way to stop those spam emails in Merak.  Does any one here knows whether Icewarp's Merak Mail offer any out-going email restriction taht I can set?  Maybe something like, if the user sends out over 50 emails of the same, the server will suspend and blacklist it for a certain period of time?.... or anyother rules that can be set for sending out emails?  

I see that they have spam fighter, but that has to do with incoming spam...  Anyone has any idea to contribute would definitely do a great help.  Thank you in advance for your kind suggestions!

Answer : Restrict Outgoing Spam (Icewarp Merak Mail Server)

I'm not familiar with Merak specifically, but if spam is coming from specific accounts, the usernames and passwords for those accounts are probably compromised. Change the passwords and inform the user of the new password. Then see if the spam stops, or slows down at least.