But perhaps I should add a not in the sign up agreement that "by signing up you agree to receive emails from us" or something like that, to be safe.
If you're in the EU, this wouldn't constitute as opt-in. The EU states that a user must specifically click a button that states "I want to receive these emails". Unless it's regarding their account. So, if the daily digest included notifications, it would be fine, but if it was just new topics, I'm not so sure. It should be fine either way, as you've said.
Has anyone done this type of stuff, either as a plugin or even as a stand alone app that simply hits the NodeBB data store (we use MongoDB, not Redis, so that matters if going that route)...
We'd like a way to get detailed user stats on a per user basis. Like how often, and it what categories, an individual is posting. We want to be able to research individual user patterns over time. Of course we can just query the DB, but this is something we'd like to see regularly both in ad hoc queries and in reports. Would be awesome to not reinvent the wheel if someone else is doing this, but I suspect no one else is. But wanted to ask before we look at making something ourselves.