Tidy It Up: How To Clean Your Email List and Boost Engagement

Tidy It Up: How To Clean Your Email List and Boost Engagement
22 July, 2021 • ... • 1207 views
Kate Shokurova
by Kate Shokurova

There are two simple but powerful reasons to spend your time on list cleaning:

  • It improves deliverability. The higher the deliverability, the greater your sender reputation and less likely for you to get blocked by email services like Gmail or Yahoo who are always on the lookout for spammers.
  • It saves you money. The majority of email service providers’ (ESP) pricing plans depend on your list volume. And you don’t want to pay for subscribers who don’t receive your emails or never interact with them.

Pandemic reminded us of how important it is to wash your hands. To have a healthy and robust email list, you also need to watch its hygiene and get rid of the toxic elements. The success of email marketing starts with the quality of contact lists. There’s little profit in spending your time on coming up with epic subject lines and super-awesome content and deals if messages fall on deaf ears or no ears at all.

Today, we’re going to talk about how to make your email list clean and keep it so. And also why it’s especially important before the iOS 15 update coming this Fall. So let’s figure out how to keep yours active and pure.

Use double opt-in

Double opt-in, also called confirmed opt-in, is when after signing up to an email list, a user has to confirm it first by clicking a corresponding button in the next email.

a simple message from Udacity

This is a simple message from Udacity that ensures that it was really you who signed up for that course. Source: Really Good Emails

Double opt-in helps to minimize such situations as misspelled and fake emails or addresses submitted by robots.

Using the confirmed opt-in is not a legal requirement but rather a recommendation. Statistics show that at the moment only about 9% of companies use double opt-in but this number is going up especially among the well-known companies that keep their lists clean proactively.

The possible reason for the popularity of the single opt-in is that with the double one the list growth process is slower. Plus, some of the users may fall off along the way. At the same time, if you use double opt-in, you get an audience that is more interested in what you offer and that is more likely to stay with you longer.

Check your lists for typos and similar things

The easiest way to increase your deliverability is to get rid of addresses that have no connection to real and willing subscribers. If you use a single opt-in (if you don’t require confirmation to become your subscriber), there’s always a possibility there are emails with typos and other kinds of mistakes on your list:

Typos usually occur as a human error, especially if a list is at least partially gathered offline.

Fearing spam, some people make use of disposable email services to create addresses that expire after a certain period of time. There’s no point in keeping such emails on your list.

Non-existent domains speak for themselves. “Eijoncnluhh” is a gibberish word and the domain eijoncnluhh.org doesn’t exist, so there’s no recipient. It also can happen if a person doesn’t want to give their real existing address.

  • Role-based and service addresses starting with contact@, info@, support@, etc.

Addresses like these are not associated with a particular individual but rather with an entire department so you can never be sure how the next employee will react to your message so it’s best to avoid such addresses altogether.

  • Duplicate contacts.

To help you get rid of such and similar emails, there are dozens of free and paid-for email validators on the web. The popular ones are:


Source: gmass.co

It’s also handy to use tools that every email service provider has, so you won’t have to go out of your account at all. For example, Selzy has the “Check contacts” tool for use when you first upload your list into the system.

That way, you will junk all this dead weight before your first mailing and improve your deliverability rates.

Once in a while, delete inactive recipients

In the previous point, we described the reasons and ways to clean up your email lists to discard unwanted contacts that don’t exist or otherwise are not right. But your lists can also grow stale even if they were strong and robust in the beginning.

Small kids think that if your salary is $30,000, then that’s what you’ll have by Christmas. In reality, you have to spend some every month. Same with email lists. If you get 3,000 new subscribers every year, that doesn’t mean you’ll have 30,000 of them in 10 years. Or, rather, you might, but only a fraction of those will be active.

There’s such a thing as a natural email database decay. There seem to be no fresh surveys on the matter but the findings of the past 5 years seem to conclude that an email database naturally decays by 22.5-30% every year. There are:

  • Inboxes that aren’t available anymore (temporarily or otherwise).
  • Inboxes with your message marked as spam (by a recipient themselves or by their email service).
  • Inboxes that are full and forgotten.

For example, if you take a look at this list in our own Selzy account, you’ll see that it has 13,208 emails but only 13,061 of them are active:

more details on the list

By clicking “more details on the list”, you can see the specifics. The number of available addresses (those reached normally) is still smaller:

this list can become better

It means that this list can become better if regularly cleaned. In Selzy, we have the “Lists cleanup” tool that’s intended for regular use. It works based on the history of your mailings. If the service sees that some of the contacts return delivery errors or their mailboxes are full, it will offer to remove them, but will not do it automatically. For example, users who unsubscribe stop receiving messages, but they still occupy their space on the list.

Every list has the "Cleanup" functionality
Every list has the "Cleanup" functionality.

OK, but these are technical issues of overflowed inboxes and such. You also need to get rid of emails whose owners are no longer interested in your services. For example, they chose to buy from another company or changed jobs and cities. Or they lost interest in your restaurant in San Diego after moving to Austin. Or they no longer need your kids’ birthday party services because their kids have grown up and now have their own ideas of what a good celebration is.

Sometimes they unsubscribe themselves, other times they don’t. One thing is clear: they don’t read your emails or interact with your website. Seasoned email marketers advise removing such contacts after a certain period of inactivity. According to the survey by Ascend2, 2-6 months of inactivity is enough reason to remove such contacts from your email marketing list:

to remove such contacts from your email marketing list

It might sound counterintuitive to remove emails that have nothing wrong with them after spending years on list growth. But you can hardly call an inactive audience a desirable one. Even if they don’t mark you as spam, they decrease your open and click rates and lower your reputation as a sender. The lesser activity from your subscribers, the more suspicious email services will be towards the authenticity of your list. It’s much better to have a small active subscriber base than a huge list of half-dead contacts.

Conduct re-engagement campaigns

Removing valid contacts? “No way!”, you might say. You have a point. The rule of thumb is that acquiring a new customer is about several times more expensive than retaining an existing one. And although some marketers have other opinions, it’s still hard to let go.

If you see that a part of your list has lost interest, first try to win them back with a re-engagement campaign. You have all the chances to turn them into your loyal customers again. By stimulating inactive subscribers, you receive extra income.

Steps to reactivate your contacts:

  1. Segment the list and filter out those who don’t open or read your emails and don’t click or shop.
  2. Understand what each specific user group wants. Offer to take part in a competition, get a discount, try a free promotional version of the product.
Animoto simply asks

Animoto simply asks whether you’re still interested in what they have to say. Source: Really Good Emails

Noom’s going further

Noom’s going further and offers a special deal to their inactive subscribers. Source: Really Good Emails

A good re-engagement campaign can yield amazing results. In one of their case studies, Inkit describes how the NatureBox company increased their revenue per customer by 60% by sending a two-sided postcard with a discount to inactive subscribers.

After conducting re-engagement campaigns, you will have one or more lists of subscribers who still won’t react. Remove them. In email marketing jargon it’s called “sunsetting”.

Segment by opens before iOS 15 update — turn to clicks after

In the previous point, we concluded that before conducting a re-engagement campaign, you need to first define the group of people that needs your attention. You can do it by using segmentation. The most popular method of segmentation before re-engagement is open rates. That is, you filter out subscribers who didn’t read your messages for a long time:

you filter out subscribers

But what about the upcoming iOS 15 update? You might’ve heard that Apple recently introduced new privacy features, namely

Apple Inc.

Mail Privacy Protection stops senders from learning whether an email has been opened, and hides IP addresses so senders can’t learn a user’s location or use it to build a profile on them.

It will concern only Apple Mail, not other email clients. But the market share of Apple Mail is 58.4% and one thing is clear — you won’t be able to rely on open rates anymore. So are those tips that include working with open rates for nothing? Well, yes and no.

It’s true that this is a major change for all email marketing. You are going to have to rely on clicks and track website activity and segment your base based on these metrics. It’s a good idea to start paying more attention to website behavior, and here we mean purchases, that’s the other primary metric you should pay attention to from now on.


The exact release date of iOS 15 is unknown, though it’s expected to come this Fall. It means you have several months during which your open rates will still be 100% valid. We recommend you segment and perform all the tests and studies involving open rates in the next couple of months while you can.

Segment by subscription date

Another idea that you can try is to segment your list based on subscription or confirmation date:

to segment your list

Contacts that have been with you longer are more likely to fall off with the passing of time so it’s a good idea to filter those ones out and start sending them special campaigns.

Bombas gives a 20% discount

Bombas gives a 20% discount to one of their long-term customers, thanking them for their “continued support”. Source: Really Good Emails

Make it easy to unsubscribe

This too may sound illogical for many marketers, and we understand your pain. List growth is one of those tasks that never go away.

Even so, adding an unsubscribe link that is easy to spot is not only good manners, in some cases, it’s a requirement. For example, CAN-SPAM Act says it’s necessary to provide “a clear and conspicuous explanation of how the recipient can opt out of getting email from you”.

It will also lower the number of spam complaints, make your lists purer, and give some thought to how to improve your campaigns (in Selzy, users have the options to indicate why they are unsubscribing).

A small link in the email’s footer is enough. But you can make more of it:

Jack Wills is not afraid

Jack Wills is not afraid to make their unsubscribe option noticeable. Source: Really Good Emails

In conclusion

You not only can but need to remove invalid addresses and inactive recipients from your list. It helps to:

  • Increase rates and deliverability.
  • Get rid of dangerous contacts with the potential to harm your rep: abandoned mailboxes, spam traps, deleted accounts.
  • Have a more engaged audience waiting for your messages.
  • Save money. We recommend you to perform list cleaning every 2-6 months. Each time, check whether your ESP of choice has some cheaper plans for you now that there are fewer contacts on your list.
22 July, 2021
Article by
Kate Shokurova
Out and about, exploring the world and its marvels. A writer and editor with 10+ years of experience, I also dabbled in all kinds of marketing and am happy to use this experience to make quality content, useful for the readers and effective for brands. I feel really passionate about helping people understand about marketing and design through easily digestible materials. Outside of working hours, I enjoy hiking, dancing, watching movies and reading books.
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