Email Marketing is different than just sending an email to contact someone who filled out a form on the website. Email marketing, for example, can be in the form of opt-in newsletters or regular updates about products and services. One-time emails can be sent to email addresses of people who told other companies that they would like to hear about related products and offers can be purchased from “third parties”. Some email address may be available from partners, as well.
More detailed information about email marketing is discussed in my Email Marketing Strategy section.