We have a user who had reported issue with outlook getting Hung while trying to edit delegates using the delegate settings in outlook. On verifying, found that one of the delegate listed is an orphaned account. The AD account doesn't have exchange properties. We had tried to remove the orphaned account from delegate list using outlook. However the outlook was getting hung and finally had to kill the session. We had used MFCMAPI to delete the orphaned account from delegate list. After deleting using MFCMAPI also, the orphaned account is still listed as delegate in the outlook delegate setting, though it is not showing while checking through MFCMAPI.
On verifying the user's properties using exchange management console, Identified that the orphaned account was included in the "send on behalf of " tab. Tried to remove the orphaned account from there, however we were getting error that "unable to find the object, make sure that it is spelled correctly or specify a different object Reason <orphaned account> is not a mailbox user, mail-enabled user or a mailcontact"
Is there any way we can remove the send on behalf of permission for this orphaned account and remove it from the delegate list of the user.