Inside Today’s Spam Filters

Dec 14, 2018

Article ImageIt used to be that marketers built campaigns by carefully selecting certain keywords while tip-toeing around other ones so they could optimize their search results and, of course, avoid spam filters. Today, you can still find lists of “words to avoid” hanging over the desks of digital marketers and content strategists. But are those lists really necessary? The evolution of the spam filter, with increasingly more sophisticated ways for determining which content is contextually relevant to the recipient, has all but eliminated the need to cross-check campaigns against those long lists of words to use and/or avoid. Yet more and more messages get stuck in email purgatory putting the marketer’s reputation at risk. What gives? Here we take a closer look at the current state of spam filters.

To understand how today’s modern spam filters work requires a closer look at how they evolved. In the beginning, blocking spam was based solely on the sending address (IP or domain). The downside to this approach is obvious as it became more and more challenging for platforms and ISPs to quickly determine which messages to let through and which to block.

It was around this time that content filters took over. They were primarily based on certain words, phrases or symbols whose incidence appeared higher and more frequently in unwanted messages. Words and symbols such as  “Buy” “$$$” “Viagra,”  and “porn” are some of the more common and obvious ones. However, that generation of spam filters often combined those negative words with other phrases, creating a somewhat all or nothing approach to messages that made it difficult to differentiate wanted from unwanted messages. 

As technology and digital marketing platforms became more intuitive based on user needs, preferences and the behaviors of senders and receivers, spam filters became even more sophisticated. Engagement-based filters got “smarter” because they took a more holistic view of the message, sender and receiver. One that took into account the profile of senders based on a variety of factors such as open rates, message headers, content, recipient complaints, list quality, and the overall reputation of the business sending the message and their use of best practices, for example.


Current Spam Filter Triggers

Today, single phrases and keywords no longer relegate a business to the spam filter. Still, many digital marketers believe the email subject field and content is more sensitive than it actually is. This causes them to overthink keywords and rewrite copy to avoid the filters. Common words such as “free” “click here” or “download now” don’t have to be avoided. Nor should they be rewritten to create awkward-sounding messages. Oftentimes, overly written phrases created to avoid spam filters are exactly what triggers the filters, relegating a message to the spam folder, and tarnishing the reputation of the sender.

Just what is considered spam these days? In general, the fundamentals still apply. This includes using a low-quality list that has not been cleaned and/or its subscribers have not clearly opted in to receive messages. Also, poor quality messages, inaccurate targeting, and the lack of solid authentication technology all continue to be key triggers for filtering. Digging deeper into the current state of spam filters, here’s what else the filters are evaluating behind the scenes.

  • If the message resembles current or known phishing scams
  • Hushbusters: These blocks of text, which are sometimes invisible to recipients, are often used in the mail structure itself in an attempt to deceive the filters
  • Hiding text in HTML comments or by using fonts, colors, or backgrounds to reduce their visibility
  • Incorrect or suspicious code
  • The image to text ratio

Technology innovations have enabled quality marketers to avoid the spam filter but it’s not just about word choices. Email marketing success is about the overall reputation of the sender and their adherence to best practices and how that forms their digital fingerprint to secure their reputation as a trusted source of content.

Since permission-based email marketing is the most effective way to attract and engage audiences, the inbox will continue to be the primary digital marketing channel. For these reasons, we’ll continue to see spam filters improve and evolve along with increasingly engaging and integrated digital marketing campaigns.

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