Many business build their lists and then believe that they can use that list to sell other products. That can be a very big mistake.
4) Keep a clean and private list. Never lose the trust of your customers that have entrusted you. If you provide your customers e-mails to others and they get spammed, many will unsubscribe to you. Remember, a good reputation will drive in more traffic and subscribers as well as strengthen the loyalty of your customers.