Give your inbox a physical checkpoint at sign-in. This independent Thetis guide covers adding a hardware key to Fastmail's two-step verification.
Before you begin
Have your password, a WebAuthn/U2F-compatible USB key, and a recovery phone ready. First-time 2FA setup requires adding that phone. For key preparation, consult the Thetis getting-started guide. No specific Thetis model has been tested for this article.
Register your key
Follow the official Fastmail registration guide alongside these steps.
- Sign in and open Settings, then Privacy & Security.
- If needed, add and verify your phone through the account-recovery options.
- Open Manage two-step verification, then Add verification device. Confirm your password if asked.
- Select the security-key option for your physical device, rather than legacy Yubico OTP.
- Connect the key by USB, touch its button when prompted, and give it a recognizable name.
Test a fresh login
Keep your existing session open. In a separate, untrusted browser session, enter your username and password, then connect and activate the key. Confirm access before closing the original session.
Prepare backup access
Add another verification device and securely store the account recovery code. Review the recovery section in the official guide.
FAQ
Does this replace my password?
No. This workflow registers a second factor, not a password-replacing hardware passkey.
What about desktop mail clients?
Third-party mail software may require an app password instead of an interactive key prompt. Create a separate app password for each application, with only the access it needs. Follow Fastmail's app-password instructions; do not paste your hardware-key PIN into a mail client's password field.
How should I prepare a spare Thetis key?
Enroll it separately rather than trying to clone your everyday key. See the Thetis backup-key guide.
Explore more
Visit Thetis Guides for more setup help.
Documentation checked: October 14, 2026. Fastmail is a trademark and service mark of Fastmail Pty Ltd. This independent tutorial does not imply sponsorship or endorsement.