I've got credential to access a server where i need to install zimbra server, prior to that I've asked to have this incoming port opened on the perimetral firewall of the isp:
After the first login I've discovered that the server wasn't able to connect to the "outside world" contacted the isp admin they said that all rules on the firewall are for incoming traffic, no outgoing traffic is permitted.
I've asket to open outgoing traffic for 25, 53,80, 443. There is the need to open other ports for outgoing traffic FROM the server?
I've readed this answer about postfix: What ports to open for mail server?
I need to know about Zimbra who use postfix but is mutch more than postfix.
I need to understand for the future, and i'll really appreciate an answer who explain why a specific outgoing port need to be opened. (53 dns, 25 smtp, 80,443 to use the internet...)