I recently migrated a multi-tenant Exchange 2010 SP3 setup to Exchange 2013 SP1, as part of a project to reuse equipment not being fully utilized and to move towards a visualized setp.
Exchange 2010 was running on Server 2008 R2 with AD DS role all on one server, I created 2 x 2012 R2 servers, one for DC & DNS, one for Exchange 2013 SP1 to have the CAS and MB role installed.
The namespace was kept, after the new CAS was succesfully allowing proxy to the old 2010 mailboxes, all client mailboxes were successfully moved to the new 2013 database.
One of the checks I did before uninstalling Exchange 2010, was that get-mailbox list showed all databases listed on the new database. All clients were working with no complaints. I've uninstalled Exchange 2010, demoted the DC, removed the member server and no it's a standalone blank 2008 R2 waiting to be wiped for a new role.
I've been told today following that, that one user can't access his mail, she is an OWA user only, upon checking ECP I can see that user no longer is listed with a mailbox. The user is still listed in the tenant AD OU along with his other colleagues whom are working fine.
Inspecting ADSI of that user shows it is still enabled with his e-mail address and pointing at the mailbox name hosted on Exchange 2013, but I have no idea where it is gone. Logging onto OWA results with. Also trying to mail enable that user does not bring that user up with a list, Exchange thinks it is already mail enabled.
A problem occurred while you were trying to use your mailbox.
Is this recoverable, I would like to understand what has gone wrong with this 1 user out of hundreds. Should I just delete the AD user and start again as I can't setup a new Exchange user with the correct SMTP e-mail address as it is currently taken.
I'm looking at what recovery options I have, including the DPM that was protecting.