As others have mentioned here, you have to be very careful. I once hired a company to send out some emails for me and they claimed to have a double opt-in list, turned out that half the people reported spam and it cause a major issue. Make sure you know what you are dealing with if you choose to go that route.
That stinks! You have to be very careful who you choose to work with. This is a good reason to stick to other methods if you are dealing with new consumers.