I wonder what the counter point to this is - the regular users who do know and are wondering why you keep telling them what you do? I wonder if a one size fits

I wonder what the counter point to this is - the regular users who do know and are wondering why you keep telling them what you do? I wonder if a one size fits all email is even a good idea? Sure it's easier, but if it wasn't that difficult to do - what about an email for users that have signed in/up within the past X days get one email and those who haven't get another (politely reminding them what it's about)? Probably need to AB test it.