We had a user that we had to migrate from one exchange server to another. The process kept breaking, so we deleted the user and recreated them, and then imported the exchange data.
Once this was done, the legacy meetings, those created prior to the recreation and import, no longer work. The meetings show up, but notifications to the user about changes say the user doesn't exist, even though the email address is identical. Further, if the user makes a meeting change or cancels, the notifications don't go out and all other users don't receive the update. However, the user in question does have the item removed from their calendar, or even moved or changed time. It's just if another organizer changes a meeting and sends an update.
So, how do we re-associate all meetings to this new user account so that updates can properly be received or sent?