Since the Can Spam Act went into effect in January 2004, unsolicited junk e-mail on the Internet has come to total perhaps 80 percent or more of all e-mail sent, according to most measures. That is up from 50 percent to 60 percent of all e-mail before the law went into effect.

To some antispam crusaders, the surge comes as no surprise. They had long argued that the law would make the spam problem worse by effectively giving bulk advertisers permission to send junk e-mail as long as they followed certain rules.

"Can Spam legalized spamming itself," said Steve Linford, the founder of the Spamhaus Project, a London organization that is one of the leading groups intent on eliminating junk e-mail. And in making spam legal, he said, the new rules also invited flouting by those intent on being outlaws.