Congress approved Monday a measure to stem the flood of unwanted e-mail. The bill, which was approved without any debate, outlaws the shadiest techniques used by Internet marketers. It now goes to the president for his signature.

According to InternetNews.com, the Can Spam Act of 2003 sets national standards for commercial e-mail senders. It puts the Federal Trade Commission in charge of enforcing the rules.

The bill makes it a misdemeanor to send spam that does not contain an opt-out offer, does not have a valid return e-mail address and does not contain notice in the subject line that it is an advertisement. Messages must also contain a valid physical address.

It also prohibits harvesting and guessing at e-mail addresses.

The measure provides for penalties of up to five years in prison for spammers.

It encourages the FTC to create a controversial do-not-spam list of e-mail addresses. FTC officials have expressed doubts about such a list, because it is so easy for spammers to conceal their identities.

Spam is the common name for unsolicited commercial e-mail -- UCE -- which can often take the form of advertisements for prescription drugs, body-enlargement supplements, online-spying software, financial products or pornography.

Last week, antispam company Brightmail reported that 56 percent of e-mail traffic in November was spam.