The Can-Spam Act received final congressional approval last week and awaits President Bush's signature. Outlawed practices will include using false or misleading transmission information, deceptive subject headings, and automated methods of registering multiple E-mail accounts for spamming. Senders of unsolicited commercial E-mail also must include their physical address and a way to opt out of future mailings.

Companies will have to update their marketing databases to note whether a person has opted out of receiving solicitations. "Anyone who's had a mailing list for any period of time may not have had that list built according to the affirmative-consent standard," says Peter Mesnik, chief technology officer of E-marketing firm IMN Inc.

Companies that rent lists from third parties should stop, says Tricia Robinson, VP of marketing at E-mail service provider Socketware Inc. Many such lists lack time-date stamps to document an individual's decision to receive messages, which could leave marketers open to running afoul of the upcoming law.