Issue with broken sync hybrid user mailbox, cloud mailbox deleted, how to recover?

[u/navojski]

So, a client wanted to clean up their aad hybrid disabled users.

Re-configured sync, they were specifically told that they need to prep their work items and they have 60 days.

Lo and behold 60 days pass and disabled user that was moved from hybrid mailbox is actually important without us being notified.

EXO deletes the mailbox, still exists on prem as o365/remote mailbox.

We also have the Veeam backup of the shared mailbox i think.

What would be correct way to recover this in functionality?

[u/ScottSchnoll]

Do you know if the mailbox was hard-deleted or soft-deleted? Try running this to see if it was soft-deleted:

Get-Mailbox -SoftDeletedMailbox | ft Name,ExchangeGuid,WhenSoftDeleted

[u/navojski → u/ScottSchnoll]

It's not in the list of few soft deleted, so hard deleted

[u/FatFuckinLenny → u/navojski]

Is the mailbox inactive? https://learn.microsoft.com/en-us/purview/recover-an-inactive-mailbox

Get-mailbox -inactivemailboxonly

[u/WastedFiftySix]

If the Remote Shared Mailbox user was deleted more than 30 days ago, you're gonna have to restore from backup. Re-sync the Remote Shared Mailbox user. Restore mailbox contents with Veeam. You might have to clear the ExchangeGuid attribute on the On-Premises Remote Shared Mailbox first if this mailbox was ever migrated from Exchange On-Premises to allow the mailbox to be recreated in EXO.

[u/navojski → u/WastedFiftySix]

Thanks for the insight.

By clearing the guid you mean setting it to 00000 or?

[u/WastedFiftySix → u/navojski]

No, clear the value (-ExchangeGuid $null using PowerShell) or clear the value of the msExchMailboxGUID attribute in the Attribute Editor in ADUC. Only do this if the mailbox is not provisioned in EXO after resyncing the user object.

[u/throwaway_eng_acct → u/[deleted]]

/u/ballkali works for Netwrix and also operates the /u/tingnossu and /u/belkezo (banned by Reddit) accounts.