Spam Filtering
What does mitigation really mean?
It is a regular occurrence that senders ask filters and ISPs for mitigation. But there seems to be some confusion as to what mitigation really means. I regularly hear from senders who seem to think that once they’ve asked for mitigation that they don’t have to worry about filtering or blocking at that ISP for a while. They’re surprised when a few weeks or even days after they asked for mitigation their mail is, one again, blocked or in the bulk folder.
Pattern matching primates
Why do we see faces where there are none? Paradolia
Why do we look at random noise and see patterns? Patternicity
Why do we think we have discovered what’s causing filtering if we change one thing and email gets through?
It’s all because we’re pattern matching primates, or as Michael Shermer puts it “people believe weird things because of our evolved need to believe nonweird things.”
Our brains are amazing and complex and filter a lot of information so we don’t have to think of it. Our brains also fill in a lot of holes. We’re primed at seeing patterns, even when there’s no real pattern. Our brains can, and do, lie to us all the time. For me, some of the important part of my Ph.D. work was learning to NOT trust what I thought I saw, and rather to effectively observe and test. Testing means setting up experiments in different ways to make it easier to not draw false conclusions.
Humans are also prone to confirmation bias: where we assign more weight to things that agree with our preconceived notions.
Take the email marketer who makes a number of changes to a campaign. They change some of the recipient targeting, they add in a couple URLs, they restructure the mail to change the text to image ratio and they add the word free to the subject line. The mail gets filtered to the bulk folder and they immediately jump to the word free as the proximate cause of the filtering. They changed a lot of things but they focus on the word free.
Then they remove the word free from the subject line and all of a sudden the emails are delivering. Clearly the filter in question is blocking mail with free in the subject line.
Well, no. Not really. Filters are bigger and more complex than any of us can really understand. I remember a couple years ago, when a few of my close friends were working at AOL on their filter team. A couple times they related stories where the filters were doing things that not even the developers really understood.
That was a good 5 or 6 years ago, and filters have only gotten more complex and more autonomous. Google uses an artificial neural network as their spam filter. I don’t really believe that anything this complex just looks at free in the subject line and filters based on that.
It may be that one thing used to be responsible for filtering, but those days are long gone. Modern email filters evaluate dozens or hundreds of factors. There’s rarely one thing that causes mail to go to the bulk folder. So many variables are evaluated by filters that there’s really no way to pinpoint the EXACT thing that caused a filter to trigger. In fact, it’s usually not one thing. It could be any number of things all adding up to mean this may not be mail that should go to the inbox.
There are, of course, some filters that are one factor. Filters that listen to p=reject requests can and do discard mail that fails authentication. Virus filters will often discard mail if they detect a virus in the mail. Filters that use blocklists will discard mail simply due to a listing on the blocklist.
Those filters address the easy mail. They leave the hard decisions to the more complex filters. Most of those filters are a lot more accurate than we are at matching patterns. Us pattern matching primates want to see patterns and so we find them.
Filtering secret sauce
It seems one of the most asked questions I hear from people is about filters and what the secret sauce is.
Read MoreCensoring email
It seems some mail to Apple’s iCloud has been caught in filters. Apparently, a few months ago someone sent a script to a iCloud user that contained the phrase “barely legal teen” and Apple’s filters ate it.
The amount of hysteria that I’ve seen in some places about this, though, seems excessive. One of my favorite quotes was from MacWorld and just tells me that many of the people reporting on filtering have no idea how filters really work.
Everybody wins!
There was a recent question on a mailing list during a discussion of spam and delivery problems. A number of folks who work in delivery were discussing how a bad address got on a list. Someone who works on the spam blocking end of things asked why do you care how a bad address got onto a mailing list?
For recipients, they usually don’t care. They just want the unsolicited mail to stop. It’s a position I have no problem with; I want the unsolicited mail to stop, too. But understanding why a particular sender is sending mail to addresses that never asked for it can be an important step in making it stop. Not by the receivers and the spam filters, they’ll just block the bad sender and move on. Or if they’re an ISP or ESP they’ll just throw the sender off for AUP violations and let the sender be somebody else’s problem.
In the broader context, though, this only changes the source of the spam. It doesn’t help the victim; the bad sender can always find another host and they will continue to mail people who never asked for that mail. And, in fairness to these senders, often they are mailing lists of mixed sources. Some of the addresses didn’t opt-in, and don’t want the mail, but a lot of addresses on their list did opt-in and do want their mail. Fixing their problem means they can mail people who want their mail. The sender is happy, the recipients are happy and the receivers are happy; everybody wins!
Everybody winning is something I can get fully behind.
You can't always get what you want
It’s a problem anyone who has done any delivery work has faced. There’s a client who is having blocklist problems or ISP delivery problems and they won’t pay any attention to what you say. They insist that you talk to the blocklist or the ISP or hand over contacts directly so they can “dialog with” someone internally. They don’t like what they’re hearing, and they hope that the answer will be different if they find a new person to talk to.
The reality is many of the people at ISPs and blocklists don’t want to talk to these types of senders. They may answer a friendly question from someone they know and trust, but sometimes not even then.
Some very large ISPs and major blocklists don’t even take sender questions. They won’t communicate with anyone about any delivery issues.
I’ve had to tell more than a few clients recently that various ISPs and blocklists weren’t interested in helping those clients with their delivery problems. There are two classes of reactions I get from clients. Some clients focus on moving forward. “OK, now what? How can we identify the issue, what data do we have and how can we figure out what the problem is?”
Other clients continue to look for ways to talk to whomever is blocking their mail. They’re convinced if they can just “explain their business model” or be told what they’re doing wrong, that all their delivery problems will magically disappear.
Needless to say those clients who focus on moving forward and looking at the information they do have have much better success resolving their delivery problems. What many senders don’t understand is the wealth of data they have that will help them resolve the issue. And even if they know it’s buried in their files, they don’t always know where to start looking or even what they’re looking for.
But that is, of course, why you hire someone like me who understands spamfiltering and email. I help senders understand how email filters work and identify what parts of their programs are likely to be responsible for delivery issues. I often find the most valuable service I provide to clients is a fresh set of eyes that can see the forest. With my help, they manage to stop obsessing unproductively about one particular symptom and focus on the underlying problems.
Senders who think the holy grail of problem resolution is speaking to the right person at an ISP or blocklist generally are disappointed, even when they hire someone who knows all the right people at the ISPs. They can’t always get what they want. But I can often help them get what they need.