[amelius]

Wouldn't it be possible for companies to simply reject e-mail addresses that end with "@relay.firefox.com"?

EDIT: Ok, it is answered in the FAQ:

> Why won’t a site accept my ⁨Relay⁩ alias?

> Some sites may not accept an email address that includes a subdomain (i.e., the “relay” portion of @relay.firefox.com) and others have stopped accepting all addresses except those from Gmail, Hotmail, or Yahoo accounts. As ⁨Firefox Relay⁩ grows in popularity and issues more aliases, our service might be placed on a blocklist. If you are not able to use a ⁨Relay⁩ alias, please let us know.