Fastmail does offer two-factor authentication with SMS: https://www.fastmail.fm/help/features_alternative_logins.html https://www.fastmail.fm/help/features_alte

Fastmail does offer two-factor authentication with SMS: https://www.fastmail.fm/help/features_alternative_logins.html https://www.fastmail.fm/help/features_alternative_logins.htm... You can also set up passwords that are only authorised for read-only access, one hour passwords, one-time passwords and Yubikey logins.