Suppress or not? Segment your email lists!

By Therese Tullgren |

List size is a measure that is ridiculous in itself. But, as an email marketer knows, it’s not about the size of the list; it’s about the quality.

The battle over when to suppress users is an old one, usually fought between those focused on list size and those on the email side who understand that inactive hurt deliverability.

It is a daily battle, with the C-levels saying, “can we open up the dormant repression – extend it – because the more we mail, the more we earn.” As an email-driven revenue business, the more people we can email, the more money we’ll make (from their perspective).

To take a step back, we know a few things about lists and email engagement and their impact on deliverability.

Lists consist of several types of emails:

  1. Spam Traps and Starter Lists – Let’s face it, these end up on everyone’s list, even with validation and hygiene and good list practices. The older your list, the more likely you are to have these because old (valid) email addresses often are used as recycled spam traps. (Many services out there, like Webbula, BriteVerify, and Fresh Address, can run your list.)
  2. Abandoned Emails – an email address is valid and was once active but is no longer. (Audience Point can help weed these out.) Again, the fact that there is no positive engagement with your post hurts your deliverability.
  3. Inactive – users are still interacting with an email from this box, possibly just not with yours. It could be because your email is in the spam folder or the user doesn’t engage. Anyway, it won’t help you to send emails to these users.
  4. Active – the list everyone wants. These users wish to access your email and actively engage with it.

An MBP (MailBox Provider) does not know if an email has been requested. All they know is what you do with it once it reaches your inbox:

  • How long it takes you to open it
  • How much time do you spend reading it
  • Do you ignore the email
  • Move it out of the spam folder
  • Do you reply to it/or do you forward it
  • You put it in a folder and save it for later
  • Mark as spam
  • Do you delete without reading
  • If you click on a link
  • Do you open it more than once?

Knowing this, we return to the question of passive suppression.

We can only make money if our mail reaches the inbox, so we must take all reasonable steps to ensure that our mail has the best possible chance of delivery. While we may be able to send to more users in the short term, the inactivity of these users will hurt our deliverability and sender reputation, which will result in more of our emails being delivered to the spam folder or filtered out entirely by MBP.

Again, this is something that all email marketers already know. So how do you juggle internal pressure with deliverability?

While several companies out there are active with segmentation and suppression, I know that many more send a single campaign to their entire list with little or no segmentation, and the statistics are reviewed in aggregate.

Every article I’ve read and searched for answers or evidence one way or another says the same thing “TEST.” It is okay to have the framework for setting up tests and an environment promoting testing. Depending on how you set up your test, this may also mean not sending any users or delaying a campaign while the test runs, which may not contribute to time-sensitive mailings. But, of course, not emailing users creates the battle in the first place.

Setting up a test that accurately measures not only engagement (opens, clicks, read rate) but “problem statistics” (complaints, unsubscribes, deletion without reading) can be challenging.

Here is my solution. Ideally, you start from a list with some form of hygiene or validation. If not, and if it’s in the budget, I highly recommend doing a batch scrub. It will help reduce the risk of emailing older/inactive users. In addition, shouldering this upfront cost helps ensure you don’t suffer a revenue crash due to the massive delivery issues that can come from Spamhaus, for example.

Take your list and build segments – active users, inactive for 30-60 days, 61-90 days, 91-120 days, etc. until you get to the point where your suppression is. While I recommend keeping your segments to about 30 days each, this depends on your business model. For example, if you only email once a month, it makes sense to open these segments.

Take your content and duplicate it for each segment. Then, update each link to maintain unique tracking, e.g., UTM-content=30-60, UTM-content=61-90, etc. It is essential because it gives you another point to correlate your data – you can use any analytics tracking on your website to determine if a user clicks through, how many of them came from your campaign, and if it was quality engagement.

It means you are emailing the same number of users as you usually do, roughly four campaigns (for example) instead of 1. Although it can be cumbersome, it is worth doing this for several campaigns over several weeks. It is worth doing on both promotional and content mailings, if only so that you have solid evidence of user retention, total revenue, and revenue per post (taking into account cost per post, if known) for each type of mailing to build your case. Doing this over an extended period also means having confidence in your results, as the curiosity effect and external factors can skew single mailings.

From here, you review positive engagement (opens and clicks), problem statistics (complaints, unsubscribes), and revenue per group.

This data is how you can build your case – active users typically have the lowest complaint rate and highest engagement, which leads to better deliverability. Again, I know this is simple, but the better your deliverability, the more revenue you can generate from email.

As you move through each segment, you’ll typically see engagement decrease and complaints and unsubscribes increase. If you were to continue emailing these inactive users, your sender reputation would continue to improve, and your overall deliverability would decrease, reducing your overall ability to generate revenue.

Although you usually see this, it may be different. This segmentation strategy is designed to give you the information you need to make informed decisions that balance business goals with email deliverability.


  • Break your segments into sections that make sense for your business and program
  • Make sure your links have unique tracking
  • Don’t just review engagement statistics
  • Review problem statistics
  • Check your deliverability and which campaigns are causing problems
  • Report on revenue per segment to build the business case

Only some understand the intricacies of email marketing – this keeps us busy and often frustrated. Internal stakeholders may need help understanding deliverability, but what they do (or should) be understood as revenue. When you can’t exclude parts of your lists to wait for test results, use segments to build your potential.

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