MJ, you raise a good question. I have seen email addresses put in italics in my own local newspaper, but I have seen them underlined as well. My own computer authority, suggests that in print it’s the designer or editor’s style option. However, if you are talking about an email in body copy on the screen, there is a definite preference for either leaving the email addresss in a regular font or for underlining it, but never putting it in italics.