Under GDPR, can someone send an email to people who 1) downloaded our app, 2) voluntarily entered their email, viewing a message that says if they do that, we can send them a newsletter about how to be more efficient with the app, and 3) selected what kind of person they are, e.g. a teacher, marketer, etc.

But it's been 10 years. Can we send them a newsletter now with an unsubscribe link? Does GDPR have an expiration date on that stuff? Yes it was affirmatively opt-in.