You can create an email address at any of our Fastmail domains. Fastmail domains are available to all users, regardless of subscription plan level.
You can also create email addresses at your own custom domain. Please note that in order to use custom domains with Fastmail, at least one admin of the account must be on a non-Basic subscription plan. You can use a custom domain purchased through any domain registrar, or you can purchase a custom domain through Fastmail.