Email marketing is directly marketing a commercial message to a group of people using email. In its broadest sense, every email sent to a potential or current customer could be considered email marketing. It usually involves using email to send ads, request business, or solicit sales or donations, and is meant to build loyalty, trust, or brand awareness. Email marketing can be done to either cold lists or current customer database. Broadly, the term is usually used to refer to:

• Sending email messages with the purpose of enhancing the relationship of a merchant with its current or previous customers, to encourage customer loyalty and repeat business,
• Sending email messages with the purpose of acquiring new customers or convincing current customers to purchase something immediately,
• Adding advertisements to email messages sent by other companies to their customers

Email marketing (on the Internet) is popular with companies for several reasons:

• An exact return on investment can be tracked ("track to basket") and has proven to be high when done properly. Email marketing is often reported as second only to search marketing as the most effective online marketing tactic.
• Email Marketing is significantly cheaper and faster than traditional mail, mainly because of high cost and time required in a traditional mail campaign for producing the artwork, printing, addressing and mailing.
• Advertisers can reach substantial numbers of email subscribers who have opted in (i.e., consented) to receive email communications on subjects of interest to them.
• Almost half of American Internet users check or send email on a typical day,[4] with email blasts that are delivered between 1 am and 5 am local time outperforming those sent at other times in open and click rates.
• Email is popular with digital marketers, rising an estimated 15% in 2009.

A report issued by the email services company Return Path, as of mid-2011 email deliverability is still an issue for legitimate marketers. According to the report, legitimate email servers averaged a delivery rate of 81%; 12% of the messages were rejected, and 7% were filtered.