Recently one of the mailbox server was not syncing with  enterprise vault server and was getting the message on the status  monitor screen as unable to synchronize with one exchange server for last 4 days.

Checked the below things:

1. Did a Force a synchronization and checked if the A7 queue is populated – No luck.
2. Checked for the archiving service mailbox status of that server(verified if this service mailbox is hidden) – No issues.
3. Checked the throttling policy – all are set to unlimited and no issues.
4. Tried to manually synchronize a mailbox  from the affected archiving Task – No Luck.
5. Brought Offline/Online Enterprise Vault Task Controller Service – No Luck
6. Restarted the affected Exchange Server and also the EV nodes – Still the same
7. Checked the moved items update summary of the affected server – no of failed updates was 0 and there was no affected mailboxes present.
8. Checked if Enterprise Vault related MSMQ queues are clear by running the below command and they were clear

Get-MsmqQueue | where {$_QueueName -like “*private*<affected” exchange server name>*”} | ft QueueName,MessageCount -autosize

But the interesting thing was that the affected server did not have any new files generated moved items summary  files right after the issue reported date.

Started looking into the event logs to see if there are any additional information to be gathered right after the issue was reported

Found this event ID 3349 right after the mailbox synchronization started happening for the affected server.

looked for this mailbox and found it was present in the affected mailbox server.

Looked into the existing entry of the legacy DN of the affected mailbox in the EV directory database by running the below

looked into the legacy exchangeDN of the affected mailbox from the Active Directory Users and computer through Attribute Editor. Both the values were different.

In this case the admin has removed the user and the mailbox but  archive remained. After some time the same user has rejoined and was created with the same UPN ,SAMID .

So when the mailbox synchronization started after the new mailbox creation EV during its synchronization of this server found this mismatch entry and stuck in the synchronization. After this it was not able to proceed with the synchronization.

Solution:

Delete the old stale legacy mailbox DN entry from the Enterprise Vault  Directory Database.

Use EnterpriseVaultDirectory
Select * from ExchangeMailboxEntry where LegacyMbxDN = ‘mention the old dn showing from the Event viewer’

Once this is done we can manually run the Synchronize Mailboxes from this affected Archiving Task  and the synchronization of all mailboxes from this affected  mailbox server will be successful.

Thanks
Sathish Veerapandian