Hi. Sorry you are having issues. When you say it does not send mail, do you mean that Relay is not sending you an email that you expect? Or do you mean that you want to send email from your Relay alias?

Hi wolfgang8741, thank you for the kind review and the feedback. For the subdomain aliases, they're really great because they're is no need to have the add-on actually generate them, you can easily create them on the fly. For example if you're on your favorite music streaming site you can just type in for the email music@yoursubdomain.mozmail.com and emails will start flowing through to that alias. Or if you're on a news site you could do newssite@yoursubdomain.mozmail.com. We created the subdomain feature for convenience in creating an alias, especially in person or when you're on a mobile app and don't have easy access to the add-on. We do encourage you to use random generated aliases as much as you can though, as a randomly generated alias has a lot more privacy benefits. Thank you!