How to send email from noreply@mydomain.com with GAE?

[Lipis via StackOverflow]

You can enable the trial (lasts for 30 days) and add as many users as you want. You can send emails to them to accept the invitations in GAE and after accepting them you can delete these users to fall back in the free version with only one user.

Please DO NOT REPLY directly to this email but go to StackOverflow:
http://stackoverflow.com/questions/18596241/how-to-send-email-from-noreplymydomain-com-with-gae/20970503#20970503