The U.S. Postal Service offers something called the National Deliverability Index. An NDF score indicates how accurately the address records mailing list in a mailing list match the latest address data maintained by the Postal Service. Mailing lists are matched using automated address verification programs. A good database company, if asked, will disclose this index to you.
It's a way that the Postal Service can help you and all of your friends in Nigeria. If you need to purchase another list of Americans who mailing list are willing to give up their private financial information in order to help you with your $30 million transfer first try the World Wrestling Federation - they may have plenty of good prospects for you. But be sure to get a sample first. Many lists companies will do that for you.
They'll send you 10 or 15 names for you to validate. Then when you ultimately get your list make sure it's in a format where you can mailing list easily import it into a database or program. Ask for the list to be sent to you that is compatible with Microsoft Excel. Or in text format that can be imported. Once imported, you've got to make sure you're doing the right follow-ups, too.