Comcast shuts some port 25: "On Monday, the company began targeting certain computers on its network of 5.7 million subscribers that appeared to be sending out large volumes of unsolicited e-mail. Spokeswoman Jeanne Russo said that in those cases, it is blocking what is known as port 25, a gateway used by computers to send e-mail to the Internet. The result, she said, was a 20 percent reduction in spam. "We're taking a precision approach . . . against the top talkers of the day," Russo said, referring to the computers being blocked. ..
For years, anti-spam activists have been pressuring Internet providers to block port 25 for all users, because it allows e-mail to be sent directly to the Internet without passing through computers operated by the service provider. Recently, spammers have infected tens of thousands of machines with malicious software code, turning them into "zombies" that operate as mail servers and launching pads for spam. Legitimate owners of these machines usually don't know their computers have been commandeered. More than 40 percent of all spam now comes from zombie machines, according to some industry estimates...
Large Internet providers vary in their approaches. America Online Inc. and Earthlink Inc. require that all residential e-mail be run through their own servers. Businesses can open accounts and process their own e-mail after being vetted. Verizon Communications Inc. also allows business customers to process their own mail.
George Webb, a group manager of Microsoft Corp.'s anti-spam unit, said getting more aggressive on blocking port 25 "can have a large impact in a short amount of time." He said the company's MSN network is reliant on cable or phone-line partners to provide its broadband service, and Microsoft is "working with them" on the problem. Webb said he thinks port 25 should be blocked by default, and customers should be required to apply for an exception. " 9:58:58 PM