Comcast, which has seen ISP giant America Online block e-mail from its subscribers bothand , acknowledged that a faulty spam filter caused the e-mail glitch that began Friday.
"For a brief period, our spam filter was blocking users from sending e-mail to .ru domains," said a Comcast representative. "That should now be corrected. There were people who were affected by this filter that was misapplied for a short period of time."
Comcast implemented the filter to thwart spammers who were using the ISP's servers to send spam with spoofed return addresses ending in .ru, the Russian top level domain.
Since Saturday, Comcast subscribers with contacts in Russia have been scrambling for information about the outage. Many took to the ISP's message boards to report their experiences and the sometimes conflicting explanations of customer service representatives.
"It took me 22 hours and a dozen e-mails to Comcast tech support to get this information" about the wayward filter, said Dmitry Stavisky, a Comcast subscriber and software developer in Wayland, Mass., who uses e-mail to communicate with clients in Moscow. "This would have been a complete disaster if I didn't have another e-mail account."
Comcast's e-mail troubles are emblematic of the problems ISPs have faced in trying to thwart spammers. ISPs have weathered criticism for letting spammers hijack their servers to send spam, and are also on the defensive from subscribers on the receiving end of increasing volumes of unsolicited commercial e-mail.