Email is no stranger to unscroupulous companies so you should be made aware what to look out for.  First of all any company that claims to have 100 or more million records that does not use Data Axle run in the other direction.  (bad lists) Data Axel who we use has 300 employees and makes 20 million calls per year. No  other company has the resources to do this. 

Where do you get your list?  This is critical to find out and if they can not provide the answer run in the other direction.  The one caveat to this is Data Axle. They are a trusted company.