Fix for MSExchange Mailbox Replication EventID 1121 Error Every Minute

Sunday, August 17, 2014
I found that an error was being reported every 60 seconds from the MSExchange Mailbox Replication service with eventID 1121 on an Exchange 2013 CU5 server.
Log Name:      Application
Source:        MSExchange Mailbox Replication
Date:          8/15/2014 12:01:15 PM
Event ID:      1121
Task Category: Request
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      SACEXCH01.Domain.local
The Microsoft Exchange Mailbox Replication service was unable to process a request due to an unexpected error.
Request GUID: 'b451acde-8d08-4a9a-a248-6bc4ca144aa2'
Database GUID: 'ed87ca06-6ce2-448a-9a3b-2c9984b067a5'
Error: Database 'aad284ae-7777-4896-93a5-cbc5e479841c' doesn't exist.
Stack trace:
   at Microsoft.Exchange.MailboxReplicationService.MapiUtils.FindServerForMdb(Guid mdbGuid, String dcName, NetworkCredential cred, FindServerFlags flags)
   at Microsoft.Exchange.MailboxReplicationService.MoveJob.ReserveLocalForestResources(ReservationContext reservation)
   at Microsoft.Exchange.MailboxReplicationService.MoveJob.AttemptToPick(MapiStore systemMailbox)
   at Microsoft.Exchange.MailboxReplicationService.SystemMailboxJobs.<>c__DisplayClassc.<ProcessJobsInBatches>b__6()
   at Microsoft.Exchange.MailboxReplicationService.CommonUtils.ProcessKnownExceptionsWithoutTracing(Action actionDelegate, FailureDelegate processFailure).
There are no open mailbox move requests, export requests, import requests, or migration batches.  I set diagnostic logging to expert, but nothing more than this single event every minute to nearly the second.

ed87ca06-6ce2-448a-9a3b-2c9984b067a5 resolves to an active database on this server.
aad284ae-7777-4896-93a5-cbc5e479841c does not resolve to any database in the org (obviously).

The fix is to remove the move request manually with the following cmdlet:
Remove-MoveRequest -MoveRequestQueue "ed87ca06-6ce2-448a-9a3b-2c9984b067a5" -MailboxGuid "b451acde-8d08-4a9a-a248-6bc4ca144aa2"
Immediately, the MSExchange Mailbox Replication event 1121 errors stopped.