Ok, so here is my problem.
Zimbra: Version 5.0.0_RC1_1538.RHEL5_64.FOSS Oct 3, 2007
I did an upgrade last night. The upgrade went very well and now we can receive email again. The problem now is the we cannot send email using our Zimbra SMTP services. From the log files it appears that Zimbra is not doing MX look ups. If the username is email@example.com then Zimbra seems to be delivering to domain.tld instead of looking up the MX record. I have tested this theory and it seems to be correct.
DNS Look ups are enabled. Anyone have any ideas?