“How do I reconnect a mailbox to another user?” is a question I’ve come across enough number of times that it makes sense to list the steps here and include a video demo.
Scenario: UserA has a mailbox. User leaves the organization. UserB joins. You need to create a new user account for UserB, and have it connect to UserA’s mailbox. (Or any situation similar to this where you want mailbox from one user to be assigned to another user. This is different from providing UserB the ability to open UserA’s mailbox as an additional mailbox – which simply requires Full Access permission to UserA’s mailbox.)
Delete the user’s mailbox from AD Users & Computers. Right-click the user account | Exchange Tasks | Delete Mailbox. Don’t worry about the mailbox data – we’re not really deleting the mailbox, just disconnecting it from UserA.
Run the cleanup agent in Exchange System Manager. Expand the Store where the mailbox resides | right-click Mailboxes | click Run cleanup agent.
This marks all disconnected/orphaned mailboxes with a red cross icon superimposed, as shown in the screenshot below.
Now you can reconnect the disconnected mailbox to another user account that isn’t (already) mailbox-enabled.
- Right-click the disconnected mailbox | click Reconnect.
- Type in the name of the user you want to reconnect it to, or click Find and look for the user.
More about disconnected mailboxes
Q. What happens to the disconnected mailboxes if they’re not reconnected?
A. The mailbox clean-up agent runs and marks a mailbox as disconnected/deleted.
By default, Exchange mailbox databases (MDBs) are configured to retain deleted mailboxes till 30 days. This makes it easy to recover any mailboxes disconnected or deleted accidentally. If deleted mailbox retention is disabled, the mailbox is purged from the database.
An exception to this rule – if the MDB is configured to not purge deleted mailboxes till the store is backed up, the mailbox lives beyond the retention period, until a backup is completed successfully.