Content Based Filters

PushSend · Apr 16, 2011

Text vs. MIME. It's a debate that'll go on for as long as there's email marketing. But when it comes to content filters, what is it that triggers them? Is it too much content? Too little? Finding the balance between those two can be frustrating to say the least. And while testing is the only way to find out for yourself, I usually find that testing = no $! And it's tough to pull the trigger on a send when you know that the revenue generated from it is going to be marginal at best. So here's a little insight into content filters.

Content based filters are incredibly complex and entire books could be written about how they work and what they look at. Of course, by the time the book was written it would be entirely obsolete. Because of their complexity, though, I am always looking for new ways to explain them to folks.

Content based filters look at a whole range of things, from the actual text in the message, to the domains, to the IP addresses those domains and URLs point to. They look at the hidden structure of an email. They look at whatâ€™s in the body of the message and whatâ€™s in the headers. There isnâ€™t a single bit of a message that content filters ignore.

Clients usually ask me what words they should change to avoid the filters. But this isnâ€™t the right question to ask. Usually itâ€™s not a word that causes the problem. Let me give you a few examples of what I mean.

James H. has an example over on the Cloudmark blog of how a single missing space in an email caused delivery problems for a large company. That missing space changed a domain name in the message sufficiently to be caught by a number of filters. This is one type of content filter, that focuses on what the message is advertising or who the beneficiary of the message is. Some of my better clients get caught by these types of filters occasionally. A website theyâ€™re linking to or a domain name theyâ€™re using in the text of the message has a bad reputation. The mail gets bulked or blocked because of that domain in the message.

One of my clients went from 100% inbox every day to random failures at different domains. Their overall inbox was still in the 96 â€“ 98% range, but there was a definite change. The actual content of their mail hadnâ€™t changed, but we kept looking for underlying causes. At one point we were on the phone and they mentioned their new content management system. Sure enough, the content management company had a poor reputation and the delivery problems started exactly when they started using the content management. The tricky part of this was that the actual domains and URLs in the messages never changed, they were still clickthrough.clientdomain.example.com. But those URLs now pointed to an IP address that a lot of spammers were abusing. So there were delivery problems. We made some changes to their setup and the delivery problems went away.

The third example is one from quite a long time ago, but illustrates a key point. A client was testing email sends through a new ESP. They were sending one-line mail through the ESPs platform to their own email account. Their corporate spamfilter was blocking the mail. After much investigation and a bit of string pulling, I finally got to talk to an engineer at the spamfiltering company. He told me that they were blocking the mail because it â€œlooked like spam.â€ When pressed, he told me they blocked anything that had a single line of text and an unsubscribe link. Once the client added a second line of text, the filtering issue went away.

These are just some of the examples of how complex content based filters are. Content is almost a misnomer for them, as they look at so many other things including layout, URLs, domains and links.
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source: Word To The Wise

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Content Based Filters

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