How List Hygiene Can Improve Deliverability

How List Hygiene Can Improve Deliverability
06 December, 2021 • ... • 833 views
Yanna-Torry Aspraki
by Yanna-Torry Aspraki

We always hear about how a good list cleaning will help with marketing statistics. If you remove inactive subscribers and focus only on engaged subscribers, your open and click metrics will grow. Simple math! As a deliverability specialist, I can say that this isn’t even the most interesting part!

Good list hygiene helps you protect your domain/IP reputation and improve your deliverability. The first step in any email marketing strategy is ensuring your subscribers receive the emails you are working so hard to craft in their inbox.

This article is contributed by Yanna-Torry Aspraki — business development & deliverability specialist at EmailConsul, a member of Women of Email association.

List hygiene and deliverability: how are these two connected?

List hygiene is something you have quite a lot of control over. It means that when you are having list hygiene issues, it is easy to penalize your domain reputation and deliverability for it.

Mailbox providers try to minimize spam/phishing and unsolicited emails in order to protect their users. With billions of emails being sent around the world daily, ISPs (Inbox service providers) work on their automated filtering to decide which emails land in the inbox, in tabs, spam, or nowhere at all. Even if different spam filters work differently, they still follow the same concepts. All ISPs look at many different types of signals in order to make their decision. This can be content, actual open rates, spam complaints, tracking links, IPs, historical reputation, and so many more.

How keeping your list clean helps avoid spam traps

Certain red flags affect your deliverability more than others, as they are clear indicators that you are not following best practices and are not a good sender. Unfortunately, list hygiene is one of the important red flags.

From ISP spam filters to blocklists such as Spamhaus, your list says a lot about you. If you are hitting spam traps (email addresses created to catch senders who buy or scrape lists) they know that you either bought a list or someone is injecting bad email addresses in your system. There are a couple types of spam traps, here are the most common ones found in lists with bad hygiene:

  • The spam traps have never been used by an actual subscriber and can’t sign up to anything because of this. So how did they end up on your list? They are literal traps to catch senders.
  • The spam traps that used to be actual subscribers a long time ago. Providers such as Spamhaus or ISPs will claim them and control the associated inbox. In this case, if you don’t clean your lists, you will keep sending to them which reflects badly on your sending practices. Why would you send emails to people who are clearly not interested in your message or are not your customers anymore? The user behind the email address doesn’t exist or use the inbox anymore. It makes it clear to them that a sender is blasting emails hoping for something in exchange, instead of sending a catered message to interested subscribers.

Does list hygiene means deleting contacts?

The answer is no. Cleaning your lists doesn’t necessarily mean deleting your contacts from your lists. Good list practices and deliverability focus on the same thing: send valuable content, to the right people at the right time, with the right frequency.

Before you even start removing subscribers or completely changing and revamping your content, you need to understand what your readers do and want. It helps you segment your lists into groups which will then receive catered content. Let’s start with first things first:

Before cleaning: how to understand and read your email statistics

When it comes to email marketing there are certain statistics you see everywhere. These include:

  • Open rates
  • Click rates
  • Bounces
  • Unsubscribes
  • Spam complaints
core metrics report example
A standard email campaign report in Selzy contains all the core metrics

Open rates

Open rates have always been quite tricky to calculate and it is important to always look at them with a grain of salt. Even without the iOS15 changes, open rates have not been a trustworthy metric for quite some time already. They are calculated based on a unique tracking pixel that is inserted into each individual email. Once a person opens an email, the mailbox provider goes to fetch all the content and images, including this tracking pixel. This is how email marketing tools know that an email has been opened.

In this iOS update guide, email marketing experts explain in detail on how this change affects email marketing.

Unfortunately, this isn’t a very precise way to measure it as different inboxes behave quite differently (i.e.: Microsoft 0365 doesn’t download images automatically on opens). Opens are great if you want to see how your subject line fairs in a recipient’s inbox, but 100% open rates with no clicks to your website or purchases, don’t make your campaign a direct success. It shows you caught the attention of your subscribers, but they didn’t perform the action you actually were looking for beyond the open.

Click rates

Click rates are better metrics to look at, as they are more precise, especially if you add a UTM link within them using a tool like Google Analytics. After recipients open the email, most want people to click through onto their website and perform a certain action, like a purchase. With UTM links in your emails, you can follow your audience all the way to when they drop off your website. This allows you to see where people got stuck or lost interest and you can remedy it for your next campaigns.

One issue in the correct click rate getting measured can come from bad deliverability or spam filters clicking on a link. This skews your statistics and it is almost impossible to differ within your email marketing tool which ones are real and which ones are fake. This is where the UTM links come in handy, you can see the user’s session and where they come from, and allows you to separate fake from true clicks.


A bounced email is an email message that gets rejected by a mail server. Certain bounces happen due to mailboxes being full or because there is a typo and the email doesn’t exist. In other cases, an email can bounce due to bad sender reputation.

bounce report
This is how the bounces report looks like in Selzy. A clear reason is given for each type of a bounced email.

Bounces, as scary as they can seem, can tell you a lot about your reputation and the hygiene of your lists. Looking at bounce rates isn’t enough, it is important to see which types of bounces you are getting.

Some emails become invalid even if they existed previously and are seen as normal behavior. If you upload a new list and your list bounces with invalid emails, that is a whole different story and can affect your deliverability and reputation.

Other times, you might have an acceptable bounce rate, but if you look deeper you might realize all your bounces come from only one service provider. It is important to then investigate and communicate with your email marketing software to see what you should do in order to work on your relationship with said mailbox provider.

Spam complaints and unsubscribes

Spam complaints and unsubscribes might have a similar result, but one is far worse than the other. Unsubscribes tell you that a person does not want to receive emails from you, while spam complaints tell the mailbox provider that your emails are unwanted.

Unsubscribes are connected to the email marketing tool you use, and they, along with you, know who has unsubscribed from which campaign. Spam complaints on the other hand are given to the mailbox provider and are not always shared back with you depending on the mailbox service provider.

Gmail, for instance, tells you the percentage of people complaining but doesn’t tell you who complained to allow you to remove them from your list. These can accumulate quite a lot over time, and if you don’t clean your lists from unengaged users, it will affect your deliverability.

Which metrics are important to keep your list clean?

When monitoring your email metrics you need to ensure that you take the time to analyze each one separately and then create a strategy based on them all as a whole. Monitoring your email statistics by understanding how they actually work, will ensure that you always make the right decisions. Keep in mind bounces and spam complaint rates remain well below 1%!

Now, let’s look at two main ways to maintain your email list hygiene.

List hygiene maintenance method 1. Segmentation

Segmentation allows you to create groups to which you can send specific content. These can be based on engagement (opens, clicks) or interests. Selzy allows you to do this very easily by creating different simple or compound rules.

segmentation tool in Selzy
This is how the Selzy segmentation tool looks like. You can segment by more than 70 criteria.

You can even use segmentation to clean your lists by creating a rule that targets all users who haven’t opened and clicked within the last X number of months. The number of months depends on your sending frequency, the more you send the smaller the number of months is.

segmentation example

Cleaning your list doesn’t mean you have to unsubscribe your recipients. You can segment unengaged users and then try to retarget them at a smaller frequency. If they still don’t engage, then you can start thinking or unsubscribing them.

Not sure how to win back the unengaged contacts? In our step-by-step re-engagement guide we explained how to do it in a smart way.

Please note: Do not delete those who have unsubscribed. You need to keep them in your CRM with their appropriate status. This way, if you were to reupload a list, their status would remain inactive or unsubscribed. 

Segmentation, when done right, can be very powerful and allow you to concentrate on specific needs parts of your list are looking for.

For example, if you sell mattresses and someone has recently bought one, trying to sell them another one by email is probably going to clutter their inbox. If you would like to continue your relationship with them, it would be important to segment them into another group where you can sell them other related products, like mattress protectors, cleaning tips, or pillows! Your customer’s journey doesn’t need to end. In this case, sending them emails at a lower frequency with valuable information will keep them engaged without affecting other subscribers’ inboxing rates.

upsell example
Dollar Shave Club offers to buy related shaving products after a purchase. Source: Really Good Emails

List hygiene maintenance method 2. Preference centers

Preference centers usually come before someone is subscribed to your list. They can be found on the subscription form and allow you to ask people what they would like to receive from you. The ultimate purpose of a preference center is to send more targeted messages to your clients from the very start of your communication

preference center example
An email preference center by Spotify. If one only wants to receive Recommended Music, but actually receives all of these… well it’s a good reason for being more than willing to unsubscribe!

The Spotify example is a classic one. In certain cases, businesses can also ask at which frequency they would like to receive emails and even lists of topics they are definitely not interested in. Every business and industry has its own distinctive features and audience and needs to ensure they cater to it.

The most important part when creating segments or preference centers is reminding yourself it needs to be created for your audience, not what you would like to share with them, as those don’t always align.

How list hygiene helps your domain reputation

Maintaining your domain reputation is extremely important. By building great relationships with your audience you are able to show inbox service providers that your email is wanted and engaging.

By segmenting and targeting your audience with specific messaging or content, you are able to inbox, engage and convert your subscribers better. It helps you organize yourself and ensure you are creating emails that don’t clutter people’s inboxes. That is what spam filters and inboxes want and it will help you inbox a lot better. It would be quite a bummer if you worked very hard on your message just to have an inbox decide your emails aren’t wanted!

Key takeaways

Here’s what to remember about list hygiene.

  • List hygiene has a direct impact on your deliverability. If your list has active subscribers that open and click your emails, this is a big sign for inbox service providers that your messages are wanted, so the deliverability will be higher.
  • It’s easier to maintain list hygiene when you ask your audience the right questions at the start and analyse your email metrics correctly.
  • Your audience wants valuable and personalized content, and segmentation allows you to target them correctly and focus on creating the right content.
  • A preference center can help maintain list hygiene right from the start, so you don’t have to do all those cleanups later.
06 December, 2021
Article by
Yanna-Torry Aspraki
Yanna-Torry is an email & deliverability specialist, consultant & speaker. Her mission is to democratize and simplify deliverability for senders, marketers and #emailGeeks alike. Yanna-Torry loves coaching and educating all kinds of senders in order to help them with email and deliverability. She is always available to geek out about email & deliverability and keeps no secret to herself.
Visit Yanna-Torry's

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