This is a piece of software that helps you to manage your email list, and it will include features such as the ability to handle bouncebacks, automate the subscribe and unsubscribe function, and personalize each message. The software should also have a tracking and reporting function, to allow you to keep track of your success rates and other important metrics.
If you choose to buy an opt-in list, there are many quality vendors that you can work with. Do a little research ahead of time, and find out how they email list acquire their email addresses: do they offer an informational newsletter or something of value in exchange for permission to receive ads? Ask about frequency--an overworked opt-in list is just as useless as a spam list.
You will do better with a list that is highly targeted. Find a list vendor who can provide you with email addresses of people who have indicated interest specifically in what you have to offer. The list may cost a little more, but your returns will pay off in the end. Email marketing is an extremely popular form of direct marketing that many businesses implement the use of in their advertising campaigns.