ASHINGTON, Oct. 22 — The Senate on Wednesday agreed to crack down on the torrent of unsolicited messages clogging the nation's e-mail inboxes, voting unanimously to outlaw the methods used by most spammers and to allow the creation of a national do-not-e-mail registry.

The action does not mean that advertisements for everything from painkillers and penis-enlargement pills to mortgages and weight-loss schemes will disappear from computers anytime soon. The House has barely begun to work on a matching bill, and even if the legislation becomes law next year, many experts have raised doubts about whether any federal action will be effective against renegade e-mailers.

But the 97-to-0 vote on Wednesday gives senators something to show the vast numbers of furious voters who have complained about the mountains of spam they encounter every morning. Many of the messages are pornographic or otherwise offensive, which increased the eagerness of lawmakers to find a way to reduce, if not eliminate, the volume of commercial e-mail.

"When this bill becomes law, big-time spamming in effect becomes an outlaw business," said Senator Ron Wyden, Democrat of Oregon and one of the chief sponsors of the bill.

The bill approved Wednesday would prohibit the use of false or deceptive headers on e-mail messages, which most spammers use to disguise their identities. All advertising messages would have to bear legitimate return addresses, as well as the abbreviation "ADV" or some similar indication of its content so that recipients could filter them away. Messages with sexual content would have to bear the equivalent of a warning label.

The bill also requires the Federal Trade Commission to begin planning a national registry of e-mail addresses of people who do not want to receive unsolicited commercial messages, similar in concept to the popular do-not-call list that was recently established to thwart telemarketers.

But the proposed registry, championed by Senator Charles E. Schumer, Democrat of New York, has produced widespread skepticism about its effectiveness, drawing a scathing comment not long ago from the chairman of the trade commission.

"If such a list were established, I'd advise customers not to waste their time and effort," Timothy Muris, the F.T.C. chairman, said in August. "Most spam is already so clearly illegitimate that the senders are no more likely to comply with new regulations than with the laws they now ignore."

But Mr. Schumer said Wednesday that Mr. Muris and others skeptical of his proposal were against any attempt to limit spam. "This is not a perfect solution," he said. "It's just the best solution we have. It will still be a lot better than what we have now."

The telephone registry requires telemarketers to compare their lists with the do-not-call list, and remove anyone who does not want to receive calls.

The spam registry, by contrast, would not be provided to spammers, who might consider it a gold mine of e-mail addresses to exploit. The technical means of making a do-not-spam list effective have not been worked out, and Mr. Schumer said the F.T.C. would have to come up with a way for e-mailers to submit their messages to the commission or another agency to be checked against the encrypted master list.

Assuming they could be caught, violators could be subject to fines of $10 per e-mail, up to $1.5 million for willful violations, and could be imprisoned for up to five years if the spam advertises a fraudulent scheme, child pornography or leads to identity theft. Those who send out more than 2,500 messages in any 24-hour period would be subject to three years in prison.

Lawmakers said they hoped the penalties would make spammers think twice before sending out millions of messages, and predicted that federal authorities would be able to track down many of the biggest and most offensive e-mailers.

Major e-mail marketers generally supported the bill — especially the provision that supersedes the growing patchwork of state antispamming laws — but they strongly objected to the do-not-spam registry.

"We think the do-not-e-mail list is a genuinely bad idea," said H. Robert Weintzen, the president of the Direct Marketing Association. He said such a list would not be respected by large spammers, but would restrict the use of e-mail by law-abiding companies. "It is simply unfair and would discriminate against the good guy and particularly the little guys," he said.

David Sorkin, an associate professor at the John Marshall Law School in Chicago and an expert on spam laws who favors banning nearly all unsolicited e-mail, objected to the bill and said it would have the opposite effect of the one intended.

"This bill legalizes spam that isn't fraudulent," he said, because it simply requires that the sender and the contents of commercial e-mail messages be accurately described. "There will be a lot more spam by legitimate marketers because they will be able to point to the federal law and say, `We are following all the rules.' "

But he said the registry had the potential to rectify that problem if the F.T.C. made it easy to use and allowed companies and Internet service providers to register entire blocks of names at once.

"If America Online could put every address at AOL.com in the registry, then you would have a law that could effectively ban spam."

That provision is not in the law, but Mr. Schumer said it was the Senate's intention that the commission allow entire domain names, like aol.com, to be blocked from spam through the registry.

To e-mail marketers, the most important part of the Senate bill was a provision that overrules most of the spam laws passed by states.

"I am thrilled beyond words," said Michael Mayor, president of Netcreations, a New York firm that assembles e-mail marketing lists. "Now we will have one standard for responsible e-mail instead of the 37 state laws we have now."

What is most significant, he said, is that the bill would overturn a California law, scheduled to take effect Jan. 1, that would ban all commercial e-mail sent to or from California that was not requested in advance. That would appear to ban the sort of marketing lists that Netcreations operates.

The Senate bill takes a different approach, hoping that spammers will not be able to withstand the combination of the registry and the requirement for legitimate return addresses and subject lines.

David Firestone reported from Washington; Saul Hansell from New York.