A private email relay helps you hide your real email address by providing you with email aliases that you can use in place of your regular email address.
You can use these email aliases for signing up on different websites, subscribing to newsletters, and whatever else you might eagerly give up your email address for.
How does Firefox Relay work?
Once you have signed up for Firefox Relay, its icon will appear in a form where you need to enter an email address. Then you select the icon to generate a new address that ends in @relay.firefox.com. You are limited to 5 email aliases.
When that app/website sends you an email, Firefox Relay receives it on your behalf and forwards it to your actual email address.
There are currently a few limitations, including that you cannot reply to emails without exposing your actual email address. But that’s OK!
Most emails received from a site, or an app, are notifications. You shouldn’t click on a link within emails if you can help it, instead go to the site in question directly from your web browser (or a saved bookmark/favorite). Then you can delete the email (and empty the trash).
Protection from Data Breaches
If you used an email alias with Firefox Relay and it ends up in a data breach, you can easily disable or delete the alias. Your primary email address is protected from the breach.