Just installed ZD on my Windows box to connect to my own mail server running Postfix/Dovecot yes, (Zimbra server is way to much of a memory hog for my Xen VPS budget).

Problem is, when I select the "Use an encrypted connection (SSL) when accessing this server" box in client POP/IMAP setup, it says SMTP connect failure. I have no problem with other clients like Outlook.

I did tcpdump packet captures on port 465 on my mail server to see what was going on. Zimbra Desktop is talking completely different language that Outlook, for sure. I see the following errors when Zimbra is connecting to port 465 on my server:

502 5.5.2 Error: command not recognized
500 5.5.2 Error: bad syntax

When Outlook connects over port 465, I can clearly see the STARTTLS command being issued, and the message being sent successfully.

It appears that Zimbra Desktop does not support TLS over port 465.

Is this true? If so, does anyone have any solutions on what to do with Postfix to get it to securely "speak" Zimbra Desktop over port 25 or 465?

Thanks in advance!