If those people respond well, you can move on to your next best list and make an offer available to the marketplace in general, people you have mailing list no relationships with. If it works there, you can use it for new customer acquisition. The key is to always test this way. It would be a mistake to take a brand new offer straight to people you have no relationship with, though you may have to try that if you don't already have a customer list.
You have to start somewhere. You may want to start by joint venturing with someone. Find someone who has a list and can endorse your offer for a split of the proceeds. You can also do this if you're already established and want to tap a list you have mailing list no relationship with. It's much better than just renting a list in your marketplace with which you have no connection to at all. A third-party endorsement can sometimes make all the difference in the world.
Before I wrap this up, let me re-emphasize that most small business people are NOT doing enough to resell to their current customers. Start doing so now, and you can easily double your profits very quickly. It's a simple, reasonable step. That's mailing list what my mentor taught me when I started working with him to add direct mail to my business in 1988, and the $2,500 a weekend I paid him -- which would be worth about $10,000 dollars now -- was worth every penny.