Outlook – Blank To: field after sending

Sent items for this user occasionally don’t have a name in the To: field (completely empty).

There are no other recipients. The email is sent successfully, but there is no way or seeing exactly who the email went to, on screen or in print (bad for filing).

Seems to be occuring when the user sends as a delegate (on behalf of her boss). Using Outlook and Exchange 2003.