The key to an effective email newsletter lies in a notion known as "permission marketing."  Your email newsletter should build goodwill with your customers and prospects, not annoy them.  Therefore, you need to obtain permission from everyone before adding them to your email marketing list.

I strongly recommend you focus the majority of your efforts on building your own house list, rather than purchasing or renting a list.  Learn how to build a profitable email marketing list leveraging proven online and offline tactics.