Once a Mandolin account has been created, you are unable to change the email address associated with that account. Should you want to log into Mandolin under a different email address, you will have to create a new one on mandolin.com. You may also delete your original account, if you wish to.
If the account you want to delete contains tickets to upcoming shows, reach out to help@mandolin.com to have them transferred to your new account so they don't get lost.