E-mail marketing is a form of direct marketing that uses email as a way to provide advertising and public fundraising. In its broadest sense, every email sent to a potential or current customer could be considered email marketing.
However, the term is generally used to refer to send e-mails with the purpose of strengthening the relationship between a merchant with its current or former clients or customers for their loyalty and retention,send e-mails with the purpose of acquiring new customers or persuade existing customers to buy something immediately,adding advertisements to e-mails sent by other companies to their customers, andsending emails on the Internet, e-mail and did not exist outside the Internet (eg electronic mail network and Fido).
Researchers estimate that U.S. companies U.S. spent $ 400 million e-mail marketing in 2006.