Sign up to sites without your real email address using Firefox Relay

This Firefox feature lets users sign up to various one-off online services without exposing their email to spam, by creating a throwaway address. — Mozilla Foundation

Most online services won't let you get access to what they're offering without you giving them at least one thing in exchange: your email address.

Then again, not everyone wants the inevitable spam that comes with signing up for that once-off hotel booking or WiFi login.