Open mailto links in Fastmail

A mailto link is a link that connects to an email address instead of a website, i.e. mailto:user@yourdomain.tld. When you click a mailto email link on another website, it will normally create a new message in your default mail application. To open these links with Fastmail:

1. Log in to your account.
2. Open the Settings → Preferences screen.
3. Click the Show advanced preferences link.
4. In the Compose & Reply Section, click the Open mailto links from other sites in Fastmail button. Note: If the button is disabled, then your browser does not support this functionality. You might need to upgrade to the latest version of Opera, Firefox, or Chrome.
5. Your browser may prompt you to allow Fastmail to open mailto links, usually in a bar at the top of the page. Click the button to allow it.

Now, any mailto link you click should open a new compose window in Fastmail. If you're not logged in at the time, you'll be prompted to log in first, then taken to the compose screen.