Spamfiltering blocks email. This is something we all know and understand. For most people, that is everyone who doesn’t manage an email server or work in the delivery field or create spamfilters, filtering is a totally unseen process. The only time the average person notices filters is when they break. The breakage could be blocking mail they shouldn’t, or not blocking mail they should.

Last week, a bunch of people noticed that Yahoo was blocking mail containing references to a protest against Wall Street. This understandably upset people who were trying to use email as a communication medium. Many people decided it was Yahoo (a tool of the elites!) attempting to censor their speech and stop them from organizing a protest.

Yeah. Not so much.

Yahoo looked into it and reported that the mail had gotten caught in their spam filters. Yahoo adjusted their filters to let the mail through and all was (mostly) good.

I don’t think this is actually a sign of filters being broken. The blocked mail all contained a URL pointing to a occupywallst.com. I know there was a lot of speculation about what was being blocked, but sources tell me it was the actual domain. Not the phrase, not the text, the domain.

The domain was in a lot of mostly identical mail coming out of individual email accounts. This is a current hallmark of hijacked accounts. Spammers compromise thousands of email accounts, and send a few emails out of each of them. Each email is mostly identical and points to the same URL. Just like the protest mail.

There was also a lot of bulk mail being sent with that URL in it. I’ve been talking to friends who have access to traps, and they were seeing a lot of mail mentioning occupywallst.com in their traps. This isn’t surprising, political groups have some horrible hygiene. They are sloppy with acquisition, they trade names and addresses like kids trade cold germs, they never expire anything out. It’s just not how politics is played. And it’s not one party or another, it’s all of them. I’ve consulted with major names across the political spectrum, and none actually implement best practices.

As I have often said the secret to delivery is to not have your mail look like spam. In this case, the mail looked like spam. In fact, it looked like spam that was coming from hijacked accounts as well as spam sent by large bulk mailers. I suspect there was also a high complaint rate as people sent it to friends and family who really didn’t want to hear about the protests.

To Yahoo!‘s credit, though, someone on staff was on top of things. They looked into the issue and the filter was lifted within a couple hours of the first blog post. A human intervened, overruled the algorithm and let the mail out.

I bet this is one of the few times anyone has seen that Yahoo does outbound filtering. Given it’s a politically charged situation, I can see why they assume that Yahoo is filtering because of politics and censorship. They weren’t though.