You've got mail, members of Congress, about 200 million pieces of it.

Nine out of 10 of those missives are e-mail, according to a report that chronicles the rapid shift from postal letters to e-mail as the means of communicating with lawmakers.

And a personal message, either online or on paper, carries more weight than the mass mailings so popular with advocacy groups, says the report from the Congressional Management Foundation, a nonpartisan group working to improve the effectiveness of Congress.

"It's the individual communication that gives a sense of who the constituent is, and is more likely to persuade members," said Kathy Goldschmidt, co-author of the report.

The report, based on a survey of 202 House and Senate offices, found that Congress received 200 million e-mail and postal mail messages in 2004, four times the 50 million total in 1995. During that period, postal mail dropped sharply, from 50 million a decade ago to about 18 million last year.

Many members have Web sites that encourage citizens to e-mail them with their opinions. The convenience of e-mails has become even more marked since the discovery of anthrax (search) in letters sent to the Capitol shortly after the Sept. 11, 2001 attacks.

Since then, all letters addressed to Congress and government agencies in Washington are required to go through a testing and decontamination process, which delays delivery by a week or more.

However, the report found that the benefits of speedy e-mail often work only in one direction. Lawmakers have generally not increased personnel to handle the jump in communications, and many still reply through postal mail.

That means it can still take anywhere from a week to a couple of months to get an answer from Washington.

Only 17 percent of House offices and 38 percent of Senate offices answer all their e-mail with e-mail, the survey found.

Brad Fitch, a co-author of the study, pointed advocacy groups to one finding: among those staff interviewed, 44 percent said individualized postal letters had "a lot" of influence when a member is undecided on an issue, but only 3 percent said that was true for form letters.

By contrast, only 15 percent said a visit from a lobbyist had "a lot" of influence