12 years? 50% or more of the emails will bounce I'm guessing. I think most people have pointed out the pitfalls already. It would have been a lot better 12 years ago if you had an opt in requirement. I always add a "subscribe to newsletter" check box on checkout so there is no question. I have used vertical response in the past. There are many benefits, easy templates, delivery rates, opening rates. Most importantly though when someone unsubscribes that is recorded in their database, future emails will not go to them. Also bounces will be ignored on future emails. Unfortunately until you send that first "blast" you'll never know what emails are good and what aren't.