You can have an e-mail address listed by registering an BlazerID in the Phonebook. Note that when you do this, your alias-based address, e.g. johndoe@uab.edu, will be listed rather than your real mailbox. This ensures people will get an address for you that is unlikely to change, even if you move to another mail server.
If you are already registered in the Phonebook but your e-mail address does not appear, or if you need to change your real mailbox address, you can use the Change Information function in the Phonebook to update your entry.