We have been approached by a service offering to construct a mailing campaign.
According to them they're able to find practically all relevant businesses in a given town, verify the addresses and weed out any closed businesses. All of this within a few hours.
Is this worth paying for and, more importantly for my position, what sort of tools are used to accomplish this?
Yes. It can be a very valuable service. And because of that-- there are a significant number of vendors in the market that provide this service. There is a wide range of quality. And there is a wide range of price.
If you live in a town of 15,000 -- it might not make sense to pay for this service. If you live in and are marketing to businesses in Houston -- I image that it could be very valuable.
The most common way you pay for the list is based on X/1000 with additional costs based on the number of variables that you choose from -- and the desired use of the list. Depending on your use you may be purchasing the use of the list rather than the actual list.
For example you could purchase the use of a email list of all real estate professionals who are licensed through a broker that has 10 or fewer agents serving zip codes with an average home price of $350,000 or more. And you would like to email that list three times.
Companies collect this information in a variety of ways. Business registration information, censure information, membership lists, web information, phone information. . . . . Many of the email lists are based on people who "opt-ed" to receive specific type of information when they registered on this site or another.
I am sure with a little bit of research you will be able to get several bids for lists that will meet your specific business need -- and evaluate the quality and cost-effectivness of the service which approached you.