Hi gang,
I have a very strange issue with a client who has recently installed two Exchange 2013 SP1 CU5 servers in a DAG configuration.
We've moved a group of pilot users over from the Exchange 2010 environment to the Exchange 2013 environment. Some of the users are experiencing an issue in which mail messages are "stuck" in the outbox folder. I've verified that in all cases, the message has actually been delivered, so it seems as if the failure is in moving the message from the Outbox folder to the Sent Items folder on the Outlook client side.
All of the users in the company are running either Outlook 2010 SP1 or SP2. They are all in online mode rather than cached mode.
The problem seems to affect only users who have a shared a mailbox, however, the messages that are effected always originate from the user's own mailbox.
There's an F5 Big-IP LTM in front of the servers providing load balancing services. It's running version 11.5.1, and is a virtual edition. It's running the latest version of the Exchange iApp (f5.microsoft_exchange_2010_2013_cas.v1.3.0). All of the web services for the environment are connecting through this reverse proxy. I considered briefly that it could be a TCP keepalive problem, but this version of the F5 iApp has a 2 hour timeout.
I haven't been able to reproduce the problem; it seems to occur at random intervals.
There are no event log entries on either the server or the client when the problem occurs.
My research so far has turned up very little. Nobody else seems to have written about having this specific problem.
Any help would be greatly appreciated!