I think through DMs is good too. One click send to all is amazing I think. Front-end: We will need an opt-in mechanism, because we don’t want to be spammy. Back-end: We need a message composer with a scheduler and draft features I think. As for the email idea, that’s more complicated.

Composer+draft - so it's more about sending custom messages for you? Not just "here is a new post" newsletter kind of thing? Scheduler - what's your specific use for it? If you explain the complicated email idea maybe we could simplify it. Send DM if needed.