Earlier today my zimbra server was hijacked and messages were being sent out appearing to be from another domain. I've captured some of the messages in the hold queue.
If my user is email@example.com can I stop my users from sending an email that appears to be from joedomain.com?
Why can my users send an email to appear as if it is coming from another domain?
Is there a way to find out how these messages were generated?
Do I need to fix something in my setup?
Thanks for your help.