There are many keys to a successful mailing: knowing what your message is, knowing who your audience is, and getting your message delivered to your audience. If you do not already have an address list for your message, then you need to put together, buy, or rent a mailing list.
The Postal Service does not keep a database of residential or business customers and does not sell address lists. However, the Postal Service has products and services that help mailers check and standardize their addresses (for instance, whether 123 MAIN is a ST, AVE, or DR) and keep their lists up to date (for example, providing ancillary services to let mailers know if addressees have moved).
There are companies that collect and sell information about consumers and businesses. You can buy or rent a mailing list from those companies. Look in the yellow pages under "lists" or "mailing lists" or do an on-line search for list providers in your area.
Refer here to learn more about how a list provider can help you target your exact audience.
Whether you maintain your own list or buy or rent a list, the next important step is to check the accuracy of the addresses on your mailing list.