Buying lists is a hotly debated topic. Most email marketers will strongly recommend against using anything other than a double opt-in name and most ESP's (Email Service providers) require that you only send correspondence to names that have been acquired via Email Database opt-in procedures. Therefore, we recommend avoiding a straight-out list acquisition. However, where data providers can be very helpful is by augmenting and correcting your existing (opt-in) contacts to Email Database help you improve segmentation. For example if your sign up forms collect email, first + last name (and perhaps company), consider using a list vendor to augment additional information that can be used to improve segmentation and audience targeting.
This might include basic demographic information Email Database like title, gender, company, Industry or number of employees in the company. Database / list vendors can also help clean up and 'normalize' your data. For example, your registration forms might Email Database collect recipient's first + last name, and company. The name "Bill" may be entered as Bil, Bill, William, etc. Good list vendors can help clean up your list for consistency. Other database vendors such as Email Database Hart-Hanks, can provide you with information about specific product interests, hardware and software infrastructure installed at a given company and much more - all of which can be used to better target your audience.
More recently, some database vendors can append social Email Database contact information. If you provide an email address, they will provide the LinkedIn, Twitter or Facebook profile / page. A Few Notes about List Quality As you grow your email Email Database marketing list, know that the list will go through natural attrition, and contacts will change or become obsolete. How do you measure the quality of the new contacts you've added to your list? Tracking and measuring the open and click-through rates are of course two key metrics to track the 'engagement' level with your contact.