I can see this has been asked before but I dont get it. I have set this client user up identical to how I have mine and mine works fine theirs doesnt. I have done everything in AD. Given full mailbox access to the account I want the person to send as. This account is called admin. I have also given send on behalf of rights. If I dont have this added then when I go in to outlook as the user they cant send emails from that user. If I add them to send on behalf the email is sent with username on behalf of. I dont want it to say this I just want it to be sent as the admin user.