I'm familiar with the concepts of firewalls and patching apps when vulnerabilities are found etc, but I couldnt call myself an expect in the subject, so, as zimbra is a package of lots of closely tied programs, I'm led to ask about it's security.
In my implimentation, I have a Zimbra server sat on the LAN, behind a 'Smoothwall' firewall. The firewall port forwards any traffic it sees on port 25 directly to Zimbra, that's the only open port that will allow traffic to hit the zimbra box. External access to users mail has not yet been turned on.
So, for someone to attack the Zimbra box, they would need to come in on port 25 and exploit something in the smtp handling side, or they would need to attack the smoothwall directly to get root and address the zimbra box in anyway they liked then. I've never heard of a smoothwall being compromised and I'm willing to class this possibility and 'impossible'
Which leaves me with just the one question, what risks of an open port 25 are there? Is it possible to gain any form of control of the server via this port? Is there anything I can do to monitor attempts at such actions?
I'm quite sure the answer to all this will be "Nope, it's quite secure and noone else has ever had a problem" but a little discussion will help when my managers see a news article and then come running at me screaming "Our data is at risk! Run for the hills!"