When a user has been moved from one Exchange Server to another, the Enterprise Vault (EV) Hidden Message is not updated
When a user has been moved from one exchange server to another, and the EV hidden message has not yet been updated because Outlook has not been closed and/or mailbox synchronization has not occurred, when attempting to manually restore or archive an item, the request is placed into the incorrect MSMQ Messaging Queue.
When the Exchange Mailbox Archiving Task attempts to connect to the mailbox, MAPI returns a MAPI_E_NETWORKERROR. EV interprets this error message as the Exchange or Global Catalog (GC) server being down and stops processing for ten minutes. The Exchange Mailbox Archiving Task will attempt to connect to the same mailbox again, and fails with the same error message.
This issue has been addressed as part of the following release:
Enterprise Vault 9.0.1 - Release Details