New York ? The premise sounds simple: To cut down on junk e-mail, simply submit your addresses to a “do-not-spam” list that marketers would have to check to avoid fines.

With more than 50 million phone numbers already on a federal do-not-call list, many e-mail users are eager for a no-spam counterpart.

But don’t hold out much hope, even if one is created. Phone and e-mail systems — and the marketers who employ them — are fundamentally different.

“It’s beyond even an apples-to-oranges comparison,” said Nicholas Graham, a spokesman for America Online Inc.

Even supporters say a no-spam list would be no panacea.

“I don’t think anyone out there is going to tell you that a do-not-e-mail registry is going to be as effective as a do-not-call registry,” said Matthew Prince, co-founder of Unspam LLC, a Chicago startup that developed technology to run such an anti-spam list.

Not that the cautions are stopping the efforts.

Sen. Charles Schumer, D-N.Y., has a bill to create a national do-not-spam list. State senates in Louisiana and Michigan have passed similar legislation, and bills have been introduced in other states. Violators could be fined — and in Michigan, even sent to jail.

An industry trade group, the Direct Marketing Assn., already keeps a no-spam list of 700,000 e-mail addresses that its members are asked to heed. Also, at least three private companies started their own no-spam lists this year. Two of them charge the public for inclusion.

But these lists have no enforcement power.

“When the do-not-call list hit 30 million names, we just said, ‘Wow,”‘ said Tom Jackson, chief executive of Global Removal Inc., which charges $5 per individual e-mail address.

Matthew Prince is co-founder of Unspam LLC, a Chicago startup company that developed technology to run an anti-spam list. He is pictured Oct. 14 near Capitol Hill. The premise sounds simple: To cut down on junk e-mail, simply submit your addresses to a do-not-spam list that marketers would have to check to avoid fines. But don't hold out much hope, even if one is created. Phone and e-mail systems -- and the marketers who employ them -- are fundamentally different.

Bryan Hunter, who runs the $9.95-a-year Remove.org, claims lists such as his help marketers better target pitches.

“They realize these are people who aren’t going to buy their products,” he said.

But John Levine, board member of the Coalition Against Unsolicited Commercial Email, dismisses such companies as toothless. Without the legal standing of a government list, such private efforts “range from naively ineffective to complete scams,” he said.

Michigan Atty. Gen. Mike Cox has threatened a deceptive-marketing lawsuit against Remove.org. The company has since toned down its Web site, but an investigation is continuing.

Meanwhile, the chairman of the Federal Trade Commission, which runs the do-not-call list, doubts whether a government-run counterpart for spam would work.

E-mail systems are spread out around the globe, and information about the e-mail sender is easy to fake. The phone network is centralized and regulated, tends to follow national boundaries and has fixed circuits that are less prone to spoofing. Together, that makes telemarketers easier than spammers to catch.

People also change e-mail addresses more frequently than phone numbers, making any no-spam list quickly old.

And while telemarketers are largely businesses pitching legitimate products, spammers are more likely to promote deceptive get-rich-quick or get-anatomically enlarged-quick schemes.

If spammers aren’t following consumer-protection laws now, they likely won’t adhere to any lists, said Bob Wientzen, chief executive of the Direct Marketing Assn.

“We’re very concerned that the American public might be sold a bill of goods,” Wientzen said, acknowledging his group’s own list has done little to stop spam.

A no-spam list also raises security issues: Just think of what could happen if a spammer got hold of such a database.

Prince and others, however, say such lists can be encrypted.