I have found the list provided by most cheap (under$200) services are very poor quality. Most of the e-Mail accounts were at one time valid but have been closed for a very long time. Many of the accounts are hotmail and Yahoo which are also opened and closed faster than a windmill spins in a tycoon. Effective e-Mail marketing requires not only valid accounts but it also requires a "filtered" and "targeted" audience.

Filtered: The members of the list have had the opportunity to opt out or get off of the mailing list and have instead chosen to stay listed.

Targeted: The products and services you sell are the products and services people on the list are interested in reading about and buying. You don't want to try to sell dust busters to a list developed by pornography web sites. Selling a dust buster would make better sales from a list developed by Home and Garden web sites.

Ask the list developer what the ratios are. Ratios of valid mail accounts to dropped. Ratio of sales to number of leads provided. Ask what the target audience of the list is. Ask how the list has been developed and how it has been tested. Ask how many copies of the list have been sold and how many more times will they be selling the same list. Ask for a 30 day money back policy or free trial period.

The one that are $30 for millions don't work and generally get your company on SPAM lists. Try USDATA in Omaha. More expensive but good results. Good luck