i have an exchange server 2010 used for receiving and sending e-mail from/to the internet. My server then was found out by spammers and they started sending massive e-mails to other people outside our domain. I stopped this by setting a filter that checks the sender and if the sender is not on the list then it deletes the message. By this way though, the server received the message and then deleted it, but never spammed other mail servers on the internet.
Is there a way to stop the attack in an earlier stage, before the server saves the message? I mean there is a lot of traffic generated by this, can i disconnect them without receiving the message?
Or do you suggest another approach?
Thank you all