Recently I had to deal with a Microsoft Outlook 2010 Outbox problem. The e-mail I send as another person was stuck in the outbox and I could wait forever before the email was send. The company had Microsoft Exchange 2010 running.
I did some investigating and came up with the following solution:
First you need to add the “send as” email account to your own account: ( I assume you already set up the right permissions.) You do not have to make a new profile.
Ok, now lets go to the Adsi Edit, and select the properties of the “send as” account:
Find the attribute msExchDelegatListLink and click on edit.
Delete the CN=*** from the person who is dealing with the problem.
Wait till everything is synced and the email while not be stuck anymore in the Outbox.