I have a Zimbra server setup to host client emails. We also have an Exchange 2010 server setup to host my company email. This has worked great for months (years in previous configurations), until last night. To my knowledge, nothing has changed.

Zimbra Log Entry
Jan 19 16:38:55 tron postfix/error[21240]: 7DB7856D11E: to=<<user@protected.com>>, relay=none, delay=88382, delays=88360/22/0/0.74, dsn=4.4.2, status=deferred (delivery temporarily suspended: lost connection with mail.myserver.com[] while receiving the initial server greeting)
It is only between our two servers, no other domians are effected on either server.

I can telnet from both servers w/o issue, and dns is setup correctly. Both resolve correctly and without issue.

Any ideas where I should start?