We are having problems sending outbound email to select domains. The emails will sit in Exchange Queue Manager w/ retry until they come back Undeliverable. We have recently changed our email configuration so that Exchange sends outbound mail instead of a SmartHost. We prefer using a SmartHost, but we were not able to send any outbound mail after a drive failure. Please let me know how to troubleshoot this issue.
I've tried the following already:
1. Enabled Message Tracking and checked history of problem emails. The following events are repeated every 15 minutes for the domain kalos-inc.com. "SMTP: Started Outbound Transfer of Message" and "Message transferred to mailserver.kalosinc.local through SMTP".
2. Enabled SMTP logging and compared information in that log to the Message tracking log.
3. Tried SMTPDIAG to test SMTP message flow and no problems during test.