Instead of waiting for weeks or longer with snail mail. You'll know which offers will be most likely end up ringing the cash register. However, be realistic, it takes time to build a relationship. You don't go on a first date and decide to get married. Get Personal Gone are the days of mass marketing.
Personalized email is key.
Make like you're your customers best friend. Emails should greet them by name, and the more you reveal what you know about them the better. Last Christmas many online retailers fell down on the job. They weren't prepared for the deluge of orders and many didn't ship in time, or ran out of hot items. Customer service counts in cyberspace too.