Changing your reply address in Outlook

First select the Accounts option from the Tools menu.

Select the account you wish to set up, and select Properties. Make sure that the General tab is selected:

By filling in the "E-mail address" with your name@domain.com email address and the "reply address" with your name@domain.com email address, any emails you send will show up on the recipient's machine with that as your return address (unless your ISP requires their domain name be used).