Anjlua, thank you for your reply, much appreciated. I have Office and Outlook 2016 and I think it may be displaying in a different way to your Office 2013. If I reply to a message that has been sent in Plain Text and I click Format and change to HTML underline works. If I receive a message in HTML and reply underline does not work however Bold and Italics work. It also looks as though if I reply and then re-send the message in HTML I am able to use Underline before re-sending the message. I think there must be a fault with the programme.