SPAM is the name given to the, unfortunately very common, act of performing e-mail marketing in receivers who do not allow the receiving of e-mails. Spam is the misuse of e-mail marketing. Even not mentioning the ethical considerations which would justify not using spam, there are very objective commercial reasons for you to stay away from it. The return is very low: for each person who reads your e-mail, there will be two hundred people unhappy with your company. Besides, you take the chance of having your emails blocked from the main e-mail providers and having your site shut down. As such, do not have illusions with the low price of e-mailing, the cost of e-mail marketing done through Spam, will eventually be much higher than the likely earnings.
See here our Anti-Spam Policy.