Overeager Spam Filters Cause Headaches

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Major ISPs are struggling to protect their customers from a growing wave of spam, but overzealous blocking can be a nuisance too, as several small ISPs have found.

Technicians for TDS Telecom, a Midwestern ISP, scrambled last week when America Online began blasting back all e-mail to AOL subscribers from TDS's 100,000 subscribers. The problem continued for days, exasperating businesses that were trying to contact customers on AOL and annoying even the most casual e-mail correspondents. Whenever a TDS subscriber e-mailed an AOL subscriber, the message was rejected with a mystifying "554 Error" code.

Frantic TDS technicians called AOL repeatedly, even through the night, but all efforts to resolve the problem were for naught.

"Whenever we called AOL we'd get no further than a Level 1 technician who'd say, 'Yeah, you're blocked. Sorry. Too bad. We can't do anything about it,'" says Nicholas Meier, manager of TDS's Internet systems support group. "It was clear AOL's techs were as frustrated by the situation as we were. They couldn't even tell us why AOL was blocking our mail. It was all automatic."

After four days of unanswered calls for help, TDS's problem resolved as inexplicably as it had begun. AOL resumed accepting e-mail from TDS subscribers. TDS techs suspect AOL's spam-busting filters decided that TDS was harmless after all, and that the service was no longer gushing spam.

All in a Day's Spam

While the impact may have been dramatic for TDS, it was merely a small battle on AOL's spam front. "We are forced to bounce up to 80 percent of all incoming Internet e-mail as suspected spam," says Nicholas Graham, an AOL spokesperson. "Our spam-blocking software is now blocking 2 to 2.4 billion messages every day."

Meier theorizes that the recent spate of viruses that turn unwitting PCs into spam-spewing monsters was to blame.

"I think AOL's spam software designates a threshold" of how much e-mail volume originating from a network is permissible, says Nathaniel Ruck, manager of data network operations for TDS. "When we go over that threshold, they start blocking our mail. It's happening to ISPs all over the country because it's an automated system that AOL has."

This isn't the first time AOL's spam-busters have globally blocked an ISP's mail. A similar incident occurred last year.

Another ISP, Charter Communications of St. Louis, has also been blacklisted by AOL's antispam software. But Charter's problems have been less horrific than TDS's, probably because Charter boasts 1.3 million subscribers versus TDS's comparatively paltry 100,000.

"There was a period last summer when we were scrambling because AOL was blocking all our e-mail," says Laurie Jill Wood, Charter's director of Internet security. "But only intermittently is it a problem anymore. I think we have a very good relationship with AOL. We see them as a partner in this war against spam."

She says AOL has been responsive to problems, noting that the giant ISP has been quick to correct erroneous information in Charter's IP addresses on a couple of occasions.

Off the Radar

For example, rogue servers that are not necessarily run by spammers are sometimes the problem.

Charter and AOL recently have identified problems involving residential customers who are illegally running a business e-mail server, Wood says. AOL's spam-blockers can detect a rogue mail server using Charter's domain name; when one is found, AOL will assume that it's a spammer's machine and refuse its mail.

AOL will not reveal details about how its spam-blocking software filters e-mail or how it decides to block mail from a certain ISP, nor will AOL comment on specific problems with ISPs. However, "before we block an ISP's mail we always try to get in touch with them and resolve the issue," spokesperson Graham says adamantly. "We're always here as a resource to help if an ISP gets blocked."

AOL is trying a number of ways to protect members from spam. For example, the ISP has also been testing a new protocol called Sender Permitted From, scanning outgoing mail for spam that uses the AOL domain name, Graham says. He and Wood agree that the problems ISPs have had with AOL blocking e-mail have nothing to do with SPF, which is still under development.

Microsoft is testing a similar identification technology to slow spam on MSN.

"Our members want us to get tough on spam," AOL's Graham says. "We're doing it in a very responsible, efficient way. We have very talented postmaster teams. We're doing the right thing ... I will tell you that [though] everyone is making mistakes, we're getting better, and we're doing the right and responsible thing."

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