How Engaged Subscribers Can Help Your Message Avoid Spam Filters

All email marketers are aware of (or should be aware of) the importance of building and maintaining a highly engaged subscriber list. By sending relevant content at the right time to people who want to receive your message, you decrease the likelihood of messages being filtered to the spam folder—which in turn increases your ROI. The criteria mailbox providers use to determine who is an “engaged subscriber” has historically been a grey area, but now we have a much better idea of what metrics mailbox providers consider important.

Each mailbox provider is unique in their filtering rules, but we do know that they all factor subscriber engagement into the equation one way or another. As would be expected, Microsoft, AOL, Gmail, and Yahoo are industry leaders when it comes to evaluating engagement metrics for their filters. When they look at engagement, they focus on specific patterns of certain sending IP addresses and domains. For example:

  • Of the mail being sent from this IP address, what is the ratio of messages sent to real accounts vs. test accounts?
  • How active are the real accounts that are being sent to? Are these subscribers frequently logging into their account and interacting with the messages they receive? Reading them? Responding to them?

Hand in hand with these patterns, mailbox providers are closely monitoring the individual engagement metrics, both positive and negative. Positive engagement metrics include (but are not limited to) messages read, messages replied to, This is Not Spam (TINS) votes, and sender domain added to address book. On the other hand, a very telling negative engagement metric is a This is Spam (TIS) vote. A This is Spam vote, often referred to as a “complaint,” is a very strong negative signal to the mailbox provider that the message sent was unwanted and has no business in the subscriber’s inbox.

Knowing how mailbox providers factor engagement into their filtering decisions gives you a leg up on your competition. However, what you do with this information is even more important. How do you make sure that the messages you are sending your subscribers are encouraging opens and reads, rather than complaints?

Send messages that are designed to engage
An engaging subject line can do wonders. If you can grab your subscriber’s attention and pique their interest with a strong subject line, you increase the likelihood that they will open your message and engage. You spend a lot of time designing content that renders well across devices, so make it count!

As an example, J.Crew Factory sent an email with a timely and compelling subject line over Labor Day. Scrolling through my email on my phone, I read “Ashley, your order now travels for free” while I was in the airport, along with the 35 million other American travelers that weekend. How timely!


Once I opened the message, the email was well designed and continued the clever travel theme to highlight their free shipping and 50% off promotions.


Send messages that align with your subscriber’s interests
It’s important to understand subscriber behavior and make sure that you messages align to their interests. Let’s say (hypothetically, of course) that I just spent a grossly inappropriate amount of money on a fancy bed for my dog (which she coincidentally will not touch with a 10 foot pole). Let’s also say that I received three follow-up emails after my purchase.

Normally, I wouldn’t mind this and would even consider it a best practice. I just made a purchase and I’m engaged with this brand, so it makes sense that they would try to strike the iron while it’s hot and keep me engaged. Unfortunately, all the messages they sent me were promoting dog beds! Now, unless they somehow knew that my very particular dog would not like the bed I chose, it is very unlikely that I am still in the market for purchasing a dog bed.

A better approach would have been to highlight other pet items that they sell: leashes, dog bowls, toys, etc. In fact, it was such an irritating experience, I ended up unsubscribing from their email program—a reaction which could have been avoided if they had sent more relevant messaging that made sense for where I was in the subscriber lifecycle.

When it comes to maintaining an engaged subscriber list, the first step is understanding how mailbox providers factor engagement patterns and metrics into their filtering methodology. From there, having a strong understanding of subscriber interests and lifecycle can help any marketer create engaging content that keeps their subscribers eagerly waiting for more.

For more information about the ins and outs of email deliverability, check out Return Path’s latest ebook, The Ultimate Guide to Email Deliverability.

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