The Microsoft Exchange Mail Submission Service (MSExchangeMailSubmission.exe) may crash intermittently on a Microsoft Exchange Server 2010 Mailbox server. Additionally, the following event is logged in the Application log:
When this issue occurs, mail submission is disrupted until the Exchange Mail Submission Service is restarted.
This issue occurs when a daily maintenance thread runs to update the watermarks of idle mailboxes. If an Exchange Server 2010 Mailbox server database has no user mailboxes or no active mailboxes, the Exchange Mail Submission Service may crash.
Note A watermark is a checkpoint that indicates the latest mailbox event that has occurred. A watermark list helps event consumers maintain a record of mailbox events that have occurred.
To resolve this issue, install the following update rollup:
2529939 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.