The Redmond, Wash., company, which has nearly 120 million e-mail customers through its Hotmail and MSN Internet services, confirmed Friday it had wrongly placed a group of Internet protocol addresses from AOL Time Warner's RoadRunner broadband service and EarthLink on its "blocklist" of known spammers whose mail should be barred from customer in-boxes.
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.
"Considering the different levels of (spam) protections on the MSN service, more spam mail is going to get blocked," she said. "But if a (spammer) is working with an EarthLink address, for example, that inevitably could cause them to be blocked."
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.
RoadRunner spokesman Keith Cocozza said that the ISP started receiving complaints last Friday that some of its 2.6 million customers nationwide could not send e-mail to MSN subscribers. Cocozza said MSN fixed the problem this week.
"RoadRunner ended up on MSN's spam blacklist, and they weren't certain why, and neither are we," he said. "We're still working on this with MSN so it doesn't happen again."
Because spam has grown to epidemic proportions, ISPs--including, EarthLink, AOL and its subsidiary RoadRunner--have gone to to stanch a problem that is affecting customers and their own networks heavily. But as more vigilant 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.
"It typically happens only by human error, due to technicians getting things wrong," said Steve Linford, president of the blocklist The Spamhaus Project. 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."
Linford runs a blocklist that is used by some smaller ISPs. But he said that if his blocklist prevented mail from EarthLink or RoadRunner, "then it would be history" at any major ISP that used it. Still, blocklists have been known to mistakenly add a range of IP addresses.
RoadRunner customers posted messages to newsgroups and the service's help pages about the problems with MSN this week.
"Something is amiss, currently some RoadRunner e-mail customers cannot e-mail MSN e-mail customers. It apparently does not (affect) everyone, but most users. Of course I asked MSN support, and they knew nothing of the problem," wrote one subscriber on the Microsoft.public.msn.discussion newsgroup.
EarthLink spokeswoman Carla Shaw said that there was a brief period over the weekend when customer e-mail was prevented from reaching MSN accounts, but the problem was fixed right away. She said that MSN did not say that the problem was spam related. EarthLink has about 5 million customers.
The MSN spokeswoman said that it is not the company's practice to block any other ISP's mail, but that the company has "been very aggressive and proactive in protecting our MSN Hotmail users from spam." Hotmail members, for example, can choose from four levels of protection: off, low, high and exclusive (which only allows mail from known senders).