WASHINGTON (Reuters) - The U.S. House of Representatives voted overwhelmingly on Saturday for a bill to outlaw most Internet spam and create a "do not spam" registry for those who do not wish to receive unsolicited junk e-mail.

Online marketers who flood e-mail in boxes with pornography and get-rich-quick schemes would face multimillion dollar fines and jail time under the measure. It passed by a vote of 392-5 at dawn on Saturday, following an all-night session of the House that was largely devoted to a separate Medicare bill.

The Senate unanimously passed a similar anti-spam bill last month, but it must assent to the House changes before the measure can become law. The Senate is expected to do so in the coming days.

Anti-spam bills have died in Congress for six years while unsolicited commercial e-mail has grown from a nuisance to a plague that threatens to derail the Internet's most popular means of communication.

Spam now makes up more than half of all e-mail, according to several surveys, and even online marketers have come to support some restrictions.

Lawmakers said spam has become a top constituent concern, and they also faced hundreds of unwanted messages daily.

Spam "cripples computer networks and makes regular e-mail checking a seemingly endless hassle," said House Energy and Commerce Chairman Billy Tauzin.

Lawmakers faced additional pressure to put a national law into place after California passed a tough anti-spam bill earlier this year. Online marketers say it would be difficult to comply with a patchwork of conflicting state laws.

The House bill, which would override state anti-spam laws, would allow businesses to send unsolicited e-mail to Internet users until they are asked to stop, an approach that some anti-spam activists say would only lead to more spam.

It would outlaw spammers' attempts to cover their tracks by requiring marketers to identify themselves clearly and avoid misleading subject lines or return addresses. Pornographic messages would have to be clearly labeled as such to allow users to more easily filter them out.

Violators would face millions of dollars in fines and up to five years in jail. The bill would not allow individuals to sue spammers.

The bill also authorizes the Federal Trade Commission to set up a "Do Not Spam" registry of Internet users who wish to receive no unsolicited e-mail at all, similar to the Federal Trade Commission's popular "Do Not Call" list.

It also would outlaw cell-phone spam, which is commonplace in Europe and Asia. Under the provision, subscribers to cell phone services would not receive text message spam unless they have provided express authorization.

America Online Inc. applauded the bill, saying it would help turn the tide against spam. "This law will be a significant weapon for the online industry in the ongoing fight to can the spam and thwart the spam kingpins," the company said in a statement.