From what I understand from reading your post, you are going to be using either a purchased mailing list or a general list of emails... I would not do this.
1. ONLY SEND EMAILS TO THOSE WHO OPT-IN TO A NEWSLETTER, AND OFFER THEM IN EVERY EMAIL A WAY TO OPT-OUT
Most email lists that you buy will include a spamtrap, and if you send an email to a spamtrap, your email will be permenantly listed in a database as spam. Beyond that your Host's IP address will be listed in blacklists as well. Sending email to those who do not follow an Opt-In Process (And that you don't have proof of Opt-In) is illegal, and you can be fined up to $100,000 for each and every email that you send.
2. BUILD YOUR OWN MAILING LIST
Start a blog, build up it's popularity and offer an opt-in procedure on the blog so users can join your mailing list. Be sure to log IP Addresses, Time/Date of Opt-In and have an Email Verification process put in place where users have to receive an email and click an activation link to confirm that they are opting in. This is called a double opt-in process and is highly recommended in accordance with the CAN-SPAM act.
