Less than 1 percent of systems that send email can be called good Netizens, according to ReturnPath, a company that compiles email reputation data. Return Path monitors 20 million IP addresses that
send email, and finds that the majority of messages come from compromised hosts sending spam. A new technique, called reputation-based filtering, can keep spam out of in-boxes. Senders are graded on
their practices, and are assigned a reputation score based on complaint rates, volume of mail sent, and senders' responses. Of the 20 million IP addresses they track, just 0.9 percent earned a
reputation score that would allow their emails to be sent to a ReturnPath client. Roughly 2.5 percent encounter problems like spam traps or too many complaints from an ISP. But a whopping 96.7 percent
score so badly that the sending computer is likely to be hacked. In fact, spam makes up 75 percent of all messages sent today, according to email security firm Postini. Much of it is sent from
hijacked computers. Pure-play spammers aren't the only ones getting blocked: up to 25 percent of commercial email never reaches its intended target, ReturnPath says. Email reputation services like
ReturnPath and Habeas make money by placing their sender-customers on "safe" lists and providing info about bad emailers to ISPs and email security providers such as IronPort.
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