Using latest release of the connector on OL 2003 SP3.
When sending email Outlook puts quite frequently a client-side message in my Inbox (from the "System Administrator"--LOL, that would be me) indicating the message was "Undeliverable" and to resend it. This has happened before, and I've always used the Zimbra AJAX Web client to verify if in fact the complete message was in the "Sent" messages folder and that there were no non-delivery messages in the Zimbra Inbox. (The connector always shows every item sent in the Sent items folder.) But doubt always persists in my mind: did the messages really get sent? Can I always infer from the presence of the message in the Zimbra Web client Sent items folder and the absence of MTA non-delivery messages in the Zimbra web client Inbox that the Outlook connector really did do the sending correctly?
What's causing these client-side "Undeliverable" messages? Synchronization issues? Timeouts? I searched in the Zimbra Bugzilla comments with such keywords as "undeliverable", but did not find anything.
Is this something just in Outlook--in which case, can I adjust the timeouts for ZCS, just as I can with POP or IMAP servers in Outlook--or something I can take up with my Zimbra email hosting company?
What particular settings of the ZCS logging mechanism would capture any problems without introducing slow-downs and timing/resource issues by itself?