I have recently been moving server hundred mailboxes from our old main store - across three new ones. Most mailboxeshave moved fine, however I have a couple that have moved to the new store but left behind a disconnected mailbox on the original store for the same user. I can't reattach it, delete it or anything - any ideas? They both have a zero size. Thanks Rob

Have you tried by running cleanup agent? Right click on Mailbox Store and "Run Cleanup Agent".

Tried that and didn't work. I think i may have found the answer in a KB940012 A stub object is left behind in the source database for certain users after a move mailbox operation is complete in Exchange 2003 Service Pack 2

If Run Cleanup Agent & Purge doesn't work aslo then try to move the mailbox back to thatsource store (where disconnected mailbox sits). Move Mailbox will prompt youthat mailbox already exists on the destination Store, and prompt you to purge, try that option. If that also doesn't work then have a look atbelow hotfix. A stub object is left behind in the source database for certain users after a move mailbox operation is complete in Exchange 2003 Service Pack 2

Yes, I had same issue with my production servers, we have installed Outlook 2007 client for one of important user and then installed the hotfix KB940012 and then move mailbox to new store. Also, in the KB 940012 they have given an workaround for this issue.