Recently I ran into an issue which is well documented for mailboxes moved to Exchange Online, but not in this case.

This issue occurred on existing online mailboxes with online archive which has been already moved to online for a long time.

Nothing appears on the DirSync logs – neither an error or an update – but on the admin portal I had an error message on the User management section stating there has been some conflict. So, using the … I was able to find the user account in error and see the following error message (as said; well known for newly moved mailbox to online services)

Exchange: Failed to enable the new cloud archive 00000000-0000-0000-0000-000000000000 of mailbox bdff422d-b76e-4468-9436-4f3c0197808a because a different archive 0e88076e-4ee0-4b1e-a634-f640fb2b2459 exists. To enable the new archive, first disable the archive on-premises. After the next Dirsync sync cycle, enable the archive on-premises again.

Exchange: An unknown error has occurred. Refer to correlation ID: f7de317a-88b6-4c80-a27e-c844fe3ff5b7

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While nothing has been done which could affect users account on Office 365, and mostly the Exchange service.

The issue appears because Outlook client was not able to connect anymore to the mailbox while accessing the mailbox using the direct URL for OWA works – I say direct URL because links to OWA from any other services were greyed. BUT user was not able to send email through OWA.

OWA is working OWA links greyed from other services
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ActiveSync was working as expected in both way receiving and sending emails.

That said, the other strange thing with this issue was, the user mailbox was correctly shown in the Exchange Control Panel as recipient and the online archive feature was correctly enabled and showing storage used by the archive.

All well known action to solved this issue were to disable the online archive, wait for directory synchronization and re enable the archive feature; BUT this was not a possible action as the mailbox has been used for few year already and the online archive had lot of content, and there is no way to export the content to be able to delete the faulty online archive.

On the On Premises Exchange, running the command Get-RemoteMailbox with FL parameter for the mailbox with the issue and it shows the all the details of this mailbox and indeed the ArchiveGuid was 00000000-0000-0000-0000-000000000000.

So, I ran the following command from the On Premises Exchange server Set-RemoteMailbox –identity <email address of the user account> –ArchiveGuid <GUID of the PREVIOUS online archive> and then ran a directory synchronization.

Then you have to wait a little until everything is replicated at the Exchange Online side.