We have a very bizarre issue in one of our M365 tenant's at the moment. I have a ticket open with Microsoft support currently but they are just ignoring it and not responding. It's been 5 days so far. Just spent 30 minutes on music on hold with them as well only to have the call get terminated. Not a great experience so far.
So, I'll preface the problem by saying our standard practice here has been when staff in one of our clients leave is to convert the user mailbox to shared and lock the account - not delete anything and then unlicense.
Well, one of our staff removed some of the unlicensed accounts in one tenant. NOT the shared mailboxes. For instance a "Search-UnifiedAuditLog -EndDate (Get-Date) -StartDate (Get-Date).AddDays(-180) -Operation "Remove-Mailbox"" doesn't return any of the accounts removed. But a Search-UnifiedAuditLog -EndDate (Get-Date) -StartDate (Get-Date).AddDays(-180) -Operation "Delete User" does.
I tried running a " Undo-SoftDeletedMailbox -SoftDeletedObject user@tennant_domain" This correctly picked up the resource was a shared mailbox and I can now see the account in EAC and see the mailbox size but: 1/ The mailbox does not show in any form in a Get-Mailbox command in powershell 2/ I'm getting a permissions issue when I either try to delete the shared mailbox or see Delegation rights. It's almost as if the mailbox is half there but not fully.
I've also tried "Get-Mailbox -Identity "guid" -SoftDeletedMailbox | Remove-Mailbox -PermanentlyDelete -Force -Confirm:$false but this is also failing.
I've tried converting the shared mailbox back to a user account mailbox but this also no luck
My theory is for some unknown reason when the unlicensed accounts were removed M365 also decided to clobber the shared mailboxes. I've kind of been able to verify this. I undeleted one user account and when licensed it also restored a mailbox for this user that appears to have been the same size as the shared mailbox was. What I need assistance with is to remove these half broken shared mailboxes. We do have backups but until I resolve the issue with the broken shared mailboxes I can't recreate and restore to them.
