People, tell a couple of services to send mail to a huge audience of the project. Our mail server no longer cope. Yes, and we decided that it is easier to place them under something more needed )
1) Letters should not be marked as spam. Ie the service should be able to unsubscribe people on request, be correctly configured and so forth.
2) No advertising of the service in the letter.
3) the Ability to substitute From and Reply-to