I've been poking around a bit more and have a few more details that might help solve this issue.
I found an error that looks like the server is trying to send to a .local name that isn't correct or something goofy like that. I think it should be reading localhost or the domain. Let me know what you guys think.
Code:
01:04:10 deferred (Host or domain name not found. Name service error for name=Zimbra-Mail.local type=MX: Host not found, try again)