Exchange Stub Mailboxes

During an Exchange 2003 to Exchange 2010 migration I came across a situation whereby the mailbox move caused a stub mailbox to be left in the Exchange 2003 mailbox store. That is, a 0 Item mailbox of a very small size (few bytes).

Running the “Get-MoveRequestStatistics’ command, it reported a “CompletedWithWarning” status. The event logs showed that the move completed successfully but was unable to delete the mailbox on the source server. This is how I ended up with a stub mailbox.

I then tried to delete the mailbox on the Exchange 2003 store. This was a VERY BIG MISTAKE. It proceeded to delete the Exchange details for the user in AD. This meant that even the Exchange 2010 server deleted the mailbox as well. I was however able to get it back by reconnecting the mailbox use the cli command ‘Connect-Mailbox’ on the Exchange 2010 server. Note that the deleted mailbox never came up on the “Disconnected Mailbox” section of the GUI.

This still left me with a stub mailbox on the Exchange 2010 server albeit with a red ‘X’ on the mailbox. Attempting to purge the mailbox gave a “… have been reconnected with an exisitng user…” error message.

The solution to getting rid of the stub mailbox ended up being setting the retention policy for deleted mailboxes to 0 days. That is in setting mailbox store->properties->limit->Keep deleted mailbox to 0 days.

Then running the “Cleanup Agent” allowed the system to delete the stub mailbox.

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