We have this website for getting consultations online: http://krcla.org/en/Get_Help , where you will see at the right that people can submit questions, and there is a pre-checked checkbox on receiving email newsletters. The form is then processed with formmail and sent to the people who work on those consultations.
Is it possible to send the formmail email to a pre-defined subscription address and have people get signed up automatically? Like firstname.lastname@example.org, for example.
There's no built in way to do so, but you can add opt-in possibilities to other forms using our API.
You should be aware, though, that the checkbox must be unchecked by default to be in compliance with our anti-spam policy.