Corrupted Legacy Mailbox fix / cleanup?

Question

I am doing a upgrade / migration from Exchange 2010->2016->2019. I have decommissioned the 2010 server and installed 2019 now. After the install of 2019 I have a mailbox showing that is tagged as legacy and corrupted.

[PS] C:\Windows\system32>get-mailbox -resultsize unlimited | Where { $_.RecipientTypeDetails -eq "LegacyMailbox" } | Set-Mailbox -ApplyMandatoryProperties  
WARNING: The object contoso.local/Microsoft Exchange System Objects/SystemMailbox{0D52FE6B-1409-46CD-B4F7-BF3C238C485E}  
has been corrupted or isn't compatible with Microsoft support requirements, and it's in an inconsistent state. The  
following validation errors happened:  
WARNING: Database is mandatory on UserMailbox.  
WARNING: Database is mandatory on UserMailbox.  
Can't apply mandatory properties on mailbox "contoso.local/Microsoft Exchange System  
Objects/SystemMailbox{0D52FE6B-1409-46CD-B4F7-BF3C238C485E}" because it is hosted on a legacy Exchange Server.  
    + CategoryInfo          : NotSpecified: (:) [Set-Mailbox], TaskInvalidOperationException  
    + FullyQualifiedErrorId : [Server=FAS-EXCH2019,RequestId=e26c8fd1-7baa-4616-b55f-a860eabec6df,TimeStamp=7/27/2022  
   3:53:58 PM] [FailureCategory=Cmdlet-TaskInvalidOperationException] D8FA54D7,Microsoft.Exchange.Management.Recipien  
  tTasks.SetMailbox  
    + PSComputerName        : fas-exch2019.contoso.local  

I am wondering if this happened during install of 2019? I had an error and it restarted the install. I can't fix or delete this in normal ways. Any suggestions on what to do?

Answer 1

Hi @Brian Hoyt ,
Considering that it's a public forum, I have covered the personal information in your post involved for privacy concern.
Please be careful to hide your personal information . Thank you!

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You could delete the mailbox that do not exist in the server by the Active Directory Users and Computers.

Please refer to the following steps :

1. open the Active Directory Users and Computers in the Active Directory.
2. Select the user under the User OU whose name is mentioned in the error.
3. Check whether the homeMDB parameter is empty or does not exist for the database.
4. If yes ,right click the account name and click “delete”.
   (Note: Please operate carefully in AD to avoid unnecessary issues)

Then you could run the following command to check if there are any other special arbitration mailboxes in your environment.

Get-Mailbox –Arbitration | ft Name, ServerName, Database –Auto  

You could get more details here:Error Solved: "Exchange 2016 database is mandatory on usermailbox" - TechNet Articles - United States (English) - TechNet Wiki (microsoft.com)

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Answer 2

To fix this issue, you may need to enter the correct value for homeMDB (the database which hosts the user mailbox). Otherwise, it would create an empty mailbox.

If you have a backup, please check which database hosts this mailbox.