Email not sending from iPhone default mail app

My email id is setup on my macbook as well as iPhone. on mackbook it works fine and I am able to send / receive emails. But on iPhone I can receive the emails only, whenever I send an email it just get rejected and showing the following error message. I have attached the screen sot. I am using same email configuration both on my laptop and mobile phone. Any suggestion would be appreciated.

The sender address has been rejected by the server.