Email Deliverability

Help! What Happened to My Email Segment Volume?

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It’s a question many email marketers ask themselves regularly: “Why does my delivered count end up with fewer subscribers than what was in my initial list?” 

I’ve heard this question several times and even asked it myself when I was on the deployment side of things.  

The TL: DR answer?  List hygiene, sunset policies, suppression lists, feedback loop data, and certain types of bounces can impact your sent volumes. 

This blog will discuss the elements that impact your segment volume and how to understand the final volume deployed.  

Read on for the deets. 

The mystery of shrinking segment volume 

Building and maintaining a healthy subscriber list is crucial for a successful email program.   

Before we dig into how and why list segment volumes can change, let’s talk about subscriber acquisition.   

Subscribers should enter your program organically, meaning they’re part of your email marketing strategy because they have chosen to be there (this is a nice way of saying don’t buy subscriber lists). 

When someone opts in to receive your emails, make sure they understand the frequency and cadence of the emails they’ll receive. Our State of Email in 2024 report notes higher spam complaints are likely to come from subscribers who forgot they signed up. Remind them in the footer that they are receiving the email because they signed up with your brand. 

How should you go about all of this? It helps to set expectations from the start to minimize customer frustration. Also, ensuring you have correct information from the subscriber is key to delivering a good consumer experience. Consider employing a confirmed (double) opt-in method by having the subscriber click through on an email while reminding them of the benefits of receiving your communications.   

List quality over quantity 

Inevitably, some of these double opt-in emails will either go into an email black hole (due to an incorrect email address on your opt-in form) or become lost due to some folks neglecting the confirmation step. That’s okay! Marketers should always prioritize quality over quantity when building mailing lists.   

I know that’s not what you’re hearing from your executive leadership teams. But hopefully, they’ll eventually realize that sending to fewer, higher-quality customers (who are actually willing to spend money with your brand) will reduce the headaches that come with sending to unengaged subscribers who drag down your deliverability. Remember: reduced deliverability (not landing in the inbox) means your messages to your high-impact customers will also end up in spam folders. The average consumer doesn’t check their junk folders often, so landing there is incredibly detrimental.    

I work with a few high-volume senders who recently removed inaccurate domains and non-engaged subscribers. Even though they reduced their sending volume, they are not seeing a decline in revenue since those email addresses weren’t converting anyway. Additionally, they saw better deliverability overall because the mailbox providers noted that they were no longer sending to bad addresses, which improved their overall engagement.   

The role of list validation

Ensuring valid email addresses enter your system and conducting ongoing list hygiene efforts is critical for strong email performance. Once a quarter, run the lesser and non-engaged addresses through a list validation tool like Validity BriteVerify.   

This will help keep you on top of things that prevent email delivery, like full subscriber mailboxes and unknown users who may have abandoned their listed address. Those subscribers bring zero value to your program.   

Sunset policies  

In addition to overall list hygiene, you’ll want to understand how your sunset policy affects segment volume. A rule that will suppress unengaged subscribers after an “x” amount of time is crucial. Solving for “x” can be challenging, but a good rule of thumb is to suppress subscribers who have not engaged with your email in the past 12 months. This timeframe can vary by industry. For example, if you’re in the car sales industry, you’ll want to keep unengaged contacts for longer since most people aren’t in the market to buy a new car every year.   

Other types of suppression lists could also impact the final delivery volume. For example, you should have a rule to suppress anyone who has unsubscribed or opted out from your program while also suppressing a list of known customers for outside reasons. 

 Feedback loops  

Your list can also shrink due to your email service provider (ESP) managing feedback loops for you. Feedback loops (FBLs) are mechanisms that provide data back to the ESP on subscribers who have marked your emails as junk or spam.   

It’s critical that this FBL processing works correctly for the major MBPs and smaller MBPs. (We offer a Universal FBL (uFBL) that can help manage those smaller providers.)  

Senders should use all available FBLs to identify and remove subscribers who have marked their email as spam or junk. Often, this process runs behind the scenes, so you may not be aware of the volume associated with it. You may expect to send to 100,000 email addresses based on the initial data pull of matched criteria, but that could decrease because of suppressed subscribers from FBL data.   

Unsubscribes vs. Complaints: Which is worse? 

 I’ll take this opportunity to reiterate: making it easier for your subscribers to unsubscribe can help your overall complaint rate. Unsubscribe actions from your subscribers are considered a neutral engagement in the eyes of the mailbox providers, whereas complaints are considered negative. This is why Google and Yahoo have implemented easy unsubscribe processes into their new requirements. If someone no longer wants to receive your email campaigns, let them opt out.   

What do bounce rates have to do with it? 

Additionally, your campaign may encounter email bounces that can change your sending vs. delivered volume.   

There are three main types of bounces: soft, hard, and block.    

Soft and block bounces can be re-tried after making changes to address any issues, but you should suppress all hard bounces moving forward. This is a function of your ESP and could account for lower-than-anticipated sent volumes. For example, soft bounces can occur if a subscriber’s mailbox is over its limit.   

A block bounce could happen if you’re having sender reputation issues—like high complaint rates—and the mailbox provider decides not to deliver your campaign to the inbox or the spam folder. These can be corrected, meaning you can attempt to send to those subscribers again. However, a hard bounce could be caused by an unknown user or invalid domain, for example. Those email addresses will never be deliverable in their current state and should be removed from future sends.    

Ideally, you would have caught some of those records in your list hygiene processing.   


As a recap, these are the items that can be impacting your initial list segmentation volume vs. what has been delivered:   

  • List hygiene   
  • Sunset policies  
  • Suppression lists   
  • Feedback loop data  
  • Certain types of bounces  

Go-to tips to keep your lists and email program healthy include:  

  • Validate lists before deployment  
  • Prioritize consistent “friendly from” names  
  • Ensure content relevance  
  • Maintain consistent frequency and avoid large changes to audience volumes  

For more tips to navigate this year’s email’s ever-evolving landscape, tune into our next episode of State of Email Live, or check out prior recordings for more great information.