You can request an alias for your @auburn.edu address at the following OIT website (click on the E-mail Alias Request link):
http://www.auburn.edu/oit/alias/
What will be the return address of the messages I send from Outlook?
Your default return address is username@auburn.edu. Faculty and Staff can request a different return address for their outgoing mail.
Log-in to the below website, and you can request the e-mail address to be changed.
https://auburn.service-now.com/it/?id=sc_cat_item&sys_id=4ed5e2b9dbfafe002fb0fba9bf9619e9