White hat all the way
Email marketing is the most cost effective way to market but you must do it right. The first thing to get right is your email list. Email marketing is only as good as the quality of your email list. You should aquire new contacts the white hat way which is to say, with the email recipients' hearty approval. You do this by giving them value in exchange for the privalege of continued communication with them.
Obtaining and nurturing people on your email list is an ongoing process. You will continuously lose people through general attrition. People move, change jobs, get married, and develope new interests. An average of 25% of your email list will become unresponsive or opt-out each year. It is a continuous effort to keep and grow your list.