The CAN-SPAM Act of 2003 authorizes a US$11,000 penalty per violation for spamming each individual recipient. Therefore, many commercial e-mail marketers within the United States utilize a service or special software to ensure compliance with the Act. A variety of older systems exist that do not ensure compliance with the Act. To comply with the Act's regulation of commercial e-mail, services typically require users to authenticate their return address and include a valid physical address, provide a one-click unsubscribe feature, and prohibit importing lists of purchased addresses that may not have given valid permission.

In addition to satisfying legal requirements, e-mail service providers began to help customers establish and manage their own e-mail marketing campaigns. The service providers supply e-mail templates and general best practices, as well as methods for handling subscriptions and cancellations automatically. They also provide statistics pertaining to the number of messages received and opened, and whether the recipients clicked on any links within the messages.

The CAN-SPAM Act was recently updated with some new regulations that went into effect on July 7, 2008.

E-mail marketing (on the Internet) is popular with companies for several reasons:

• A mailing list provides the ability to distribute information to a wide range of specific, potential customers at a relatively low cost.
• Compared to other media investments such as direct mail or printed newsletters, e-mail is less expensive.
• An exact return on investment can be tracked ("track to basket") and has proven to be high when done properly. E-mail marketing is often reported as second only to search marketing as the most effective online marketing tactic.
• The delivery time for an e-mail message is short (i.e., seconds or minutes) as compared to a mailed advertisement (i.e., one or more days).
• An advertiser is able to "push" the message to its audience, as opposed to website-based advertising, which relies on a customer to visit that website.
• E-mail messages are easy to track. An advertiser can track users via autoresponders, web bugs, bounce messages, unsubscribe requests, read receipts, click-throughs, etc. These mechanisms can be used to measure open rates, positive or negative responses, and to correlate sales with marketing.
• Advertisers can generate repeat business affordably and automatically.
• Advertisers can reach substantial numbers of e-mail subscribers who have opted in (i.e., consented) to receive e-mail communications on subjects of interest to them.
• Over half of Internet users check or send e-mail on a typical day.
• Specific types of interaction with messages can trigger other messages to be delivered automatically, or other events, such as updating the profile of the recipient to indicate a specific interest category.
• E-mail marketing is paper-free (i.e., "green").
• Tracking and response metrics enables tuning and optimisation of the E-mail marketing channel by a process of testing different variants and calculation of statistically significant results.