I strongly advise against spam - for many reasons, but if you are planning on building a lasting business that people know, love and trust, you do not want the reputation of a spammer.
In terms of email services, I like Aweber. It's permission-based and allows you to build a strong list based on those who have given you permission to market to them - this is the group of people that are also most likely to purchase from you and tell other people about you (which is the point, is it not?).
Aweber also allows you to create a great an auto-response sequence. If you pack your auto-response sequence full of information that your subscribers want to hear they will READ your emails!
If you want an example, we offer a popular email free course about how to answer this question: "Why should customers do business with you?" Subscribers to that course get a new lesson every 4 days. It's good content and gets read. This builds our reputation and creates loyalty. Very effective. You can subscribe by going to www.NaturalMarketingBlog.com
A guess the point is this: take the time and put in the effort to build a list of loyal subscribers if you want email marketing to be successful.
Oh, also - I would suggest you read *any* and all of Seth Godin's books.