Don't overload prospects with your offers. Include useful information with your offer. Use of one's own database of prospects. It doesn't overload the customers with offers, but rather presents them in a subtle way. Gives prospects an option of opting-out.
Information is requested by the customer.
Gives useful information. Delivered to as many people as possible in the shortest time needed. Turns prospects into buyers. Your prospects send a blank email to your autoresponder address containing information about you and your business. These are mailing lists your prospects subscribe to in order to receive your ads.