After a migration of Exchange 2003 to Exchange 2007 I noticed some mailboxes were marked as Linked Mailbox. This is kinda weird as this should mean they are linked to another forest. This wasn’t the case. These were just mailboxes in the same forest as all others.

To resolve this issue there are 2 options. These options are not fully tested (at my part) so please feel free to add your findings. Mailbox settings are not lost if you try the first option (Out of Office assistant for example):

Option 1

1. Lookup on which storage group/mailbox store the user is connected at this moment (if there is more than 1 storage group)
2. Disable the user for Exchange (command-shell): Disable-Mailbox -Identity “Full Username”
   This will remove all Exchange properties on the User account in Active Directory (you will be prompted to delete all info). The mailbox will not be deleted. The connection between the account and mailbox will be removed.
3. Reconnect the mailbox to the account.Use the command-shell :
   Connect-Mailbox -Identity “Full Username” -Database “Server\Storage Group\Mailboxstore” -User “Domain\username”
4. Check the properties of the mailbox.

Option 2

You can edit the mailboxes AD attribute RecipientTypeDetails. This appears to be unsupported so please don’t use this in a production environment!

For more info on the property : http://blogs.technet.com/benw/archive/2007/04/05/exchange-2007-and-recipient-type-details.aspx