First thing I would do is from the remote machine telnet to the ports to verify you can connect. If you can not then there is a network issue or a firewall stopping you.
Example (replace zimbraserver.test.com with your mail server):
Telnet zimbraserver.test.com 110 (you should receive a POP3 banner)
Telnet zimbraserver.test.com 465 (there will be no banner but the telnet window will stay up)
If your telnet session times out or immediately disappears then the client machine can not connect either because of a firewall or network issue. If you are using a hostname then it might be DNS, try the IP address instead of the hostname.
I would also check your maillog to verify the remote machine is establishing a connection. |