Send on Behalf of Does not appear in From:

We have Exchange 2013 and Outlook 2010 clients. I have setup Send on behalf for a specific user and it works correctly when the messages are sent within the organization. If the user sends a message to people outside the organization and uses the sent on behalf option the recipient does not see the "send on behalf of" in the from field. It show as if it was send directly from the senders mailbox