Your username is the email address you use to log in to your FastMail account. If you change your mind, we allow this to be renamed once, after upgrading your account. Please be careful in your new selection, as we only allow it to be renamed again under exceptional circumstances (you will have to contact our support team if you have already renamed your account and need to so so again).
To rename your account:
Please note that when you rename your account, your old address will be automatically added as an alias. This means that you can continue to send/receive emails using your old address as well.
If you don't want to receive emails sent to your old address, you can delete the alias on the Settings → Aliases screen.
Due to an internal technical limitation, we cannot allow dots (
.) in usernames at FastMail domains. However, we do support them in usernames at your own domain, in a business or family account. We also allow them in aliases, even at FastMail domains.
See the instructions on the business/family pages for renaming an account.