In any ad you can also include a "mail-to" link to an auto-responder message that you have developed regarding a specific product you are selling. You can set up an unlimited number of messages that can be automatically delivered to your prospect at predetermined intervals.
It has been said that it takes up to seven contacts to sell a person. With that in mind, why not set up a sequence of ten messages to sell a particular product. You set up it up once and the auto-responder makes the recurring contacts.
There are now dozens of free auto-responders out there that you can use: just type in "free auto responder" into any search engine. Many also include personalization features so that when someone gets your e-mail it automatically has their name in it. I use www.getresponse.com for my list.