MSN blocks emails from rival ISPs

Microsoft's MSN has admitted that its email services have been blocking incoming mails from rival ISPs earlier this week, after their networks were banned as sources of junk mail.

MSN has nearly 120 million email customers, including those using the vastly popular Hotmail service, but last week those users may have noticed a cessation of emails from friends and relatives sending mail from AOL's RoadRunner broadband service and EarthLink addresses, as these had been added en masse to its 'blocklist' of known spammers.

Once notified of the error by the two ISPs, MSN moved the IP addresses "over to a safe list immediately," according to a Microsoft spokeswoman.

MSN and Hotmail use spam-filtering software and services from San Francisco-based Brightmail, whose techniques focus on the message's content when filtering spam. Beyond that, MSN's spam-abuse team compiles its own list of IP addresses that are known to generate unsolicited junk messages, and it blocks all messages from them.

Because spam has grown to epidemic proportions, ISPs have gone to great lengths to stanch a problem that is affecting customers and their own networks heavily. But as more vigilant antispam measures are employed, legitimate messages are increasingly caught in the net, causing frustration at both ends.

Antispammers say that MSN's action in blocking the rival ISPs was likely caused by human error.

Steve Linford, president of blocklist The Spamhaus Project, said: "It typically happens only by human error, due to technicians getting things wrong." said. He added that EarthLink and RoadRunner are known for having good spam-abuse teams that work to prevent people from using their networks to send junk mail. But he said that some spam inevitably slips through.

"The enormous spam problem is causing this," said Linford. "We're more likely to see errors and large providers getting blocked with ISPs, as they maintain their own blacklist, because the possibility for human error is enormous."