If you disable a user’s mailbox in Exchange 2010 it moves to the Disconnected Mailbox Container under Recipient Configuration in Exchange. Now when you re-connect the mailbox to the AD user and you try send an email to the account you get the following error:
#554-5.2.1 mailbox disabled 554 5.2.1 STOREDRV.Deliver.Exception:AccountDisabledException.MapiExceptionMailboxDisabled; Failed to process message due to a permanent exception with message Cannot open mailbox /o=First Organization/ou=Exchange Administrative Group.
Run the following command from Exchange powershell:
- Clean-MailboxDatabase “databasename”
After this you should be able to send mails to the user and login to the mailbox.
Hope it helps.