Unable to connect a disconnected mailbox – User not found error when trying to connect a mailbox to a user in Exchange

We’ve had a few instances where we need to disconnect a mailbox and reconnect it to a new user account for a user. This should be easy right? Well not always.

It’s happened more than once where we try to use the Exchange Management Console to connect the mailbox to the user account but Exchange can’t find the user account. Have a look in Active Directory and the account shows up. You then try to connect the mailbox to the user account using the Exchange Management Shell with the same results. user not found.

See below on how to get this issue resolved:

1. Open adsiedit.msc (start, run and type adsiedit.msc)
2. Search for the user
3. Open the properties for the user you need to connect the mailbox to
4. Search for the msExchRecipientTypeDetails property
5. For users, change the value from 1 to 0

Wait for replication and then reconnect the mailbox to the user account.

Thanks goes to our colleague Waleed for sharing this with us.


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