List Building

Email Scrubbing: Why it’s important for list hygiene, and How to do it correctly!

Cai EllisRobert Brandl

By Cai & Robert

transactional email examples

We all know that the potential ROI of an email list isn’t in the quantity of subscribers. It’s the quality of your subscribers that makes a difference.

And that’s why a small email list with quality subscribers can outperform a large email list filled with invalid emails and unengaged subscribers.

But, how do you make sure that your email list consists of high quality, active subscribers?

Well, say hello to email scrubbing and wave goodbye to inactive users and unengaged subscribers who don't get involved or convert.

Email scrubbing will enable you to clean your list of low-value email addresses and keep only quality leads who are more likely to engage with your emails and convert. Plus, you'll have fewer spam complaints and a better sender reputation.

Let’s dive into more details about email scrubbing: what it is, why it’s important for email list hygiene, and how to use it for more successful email marketing campaigns.

What is Email Scrubbing?

Just like the name implies, email scrubbing is the process of scrubbing clean your email list to remove inactive subscribers, and invalid and duplicate email addresses from your list.

These subscribers do not open your emails, let alone engage and convert. Some of the people don’t even receive your emails at all. Worse still, others may mark your email as spam, which can have a very bad effect on your deliverability. All of these affect the success of your email marketing campaigns.

Hence, the goal of email scrubbing is to keep your email list updated and ensure that you’re sending emails to only valid and engaged subscribers who are genuinely interested in your offers.

Continue reading to learn the benefits of email scrubbing and a clean email list.

Why you should periodically scrub your email list

Besides being an essential aspect of email list management, here are some reasons you should clean your email list periodically.

1. Reduces email marketing costs

Most ESPs (Email Service Providers) charge based on the number of subscribers and/or emails sent. So, maintaining a large email list is more expensive than a medium or small list.

And that’s okay if all the subscribers on your list are valid, active, and engaged. But if you have a large email list full of inactive, invalid, and unengaged email addresses, then it's a waste of money.

Email scrubbing removes these subscribers, thereby reducing your email list size and the cost of maintaining it. It may seem like nothing, but this extra cost can add up quickly.

For instance, let’s say you have an email list of 1800 subscribers, but more than half are inactive, invalid, or unengaged, you’ll be incurring a cost of $22.50/month using MailerLite. On the other hand, if you scrub the list to retain 900 engaged subscribers, you can use MailerLite for free!

So scrubbing your email lists is a quick way to stop wasting money sending emails that won't provide any benefit to your business and, as we’ll see next, may even harm your company!

2. Improves email sender reputation

Scrubbing your list reduces bounces, eliminates spam traps, and prevents spam complaints. This helps you avoid triggering email providers SPAM filters and improves your sender reputation. Here’s how…

When you scrub your email list, you get rid of invalid or inactive email addresses that cause email bounce. And, inactive emails which are used as spam traps to identify and catch spammers are also eliminated. Subscribers who aren’t interested in your emails and are likely to “mark as spam” are removed too, so you'll get fewer spam complaints.

Hence, your clean email list will consist of only valid email addresses and active subscribers who engage with your emails. This signals to ESPs and ISPs that you’re not a spammer and improves your sender reputation.

3. Increases email deliverability

With reduced bounce rate, spam complaints, and spam traps (which improves your email sender reputation), your email deliverability rate will also increase. This means that the chance that your emails will be delivered to your subscribers will be higher.

And, when the majority of the subscribers remaining after an email scrub are engaging with your emails, ISPs and ESPs will see your email as important. Thus, they’ll ensure that your emails are delivered to their subscribers inboxes (and not the spam folder).

4. Improves subscribers engagement rates

Engagement rates include metrics like open, click through, and conversion rates. Scrubbing your email list can improve these email metrics, as you’ll be left with subscribers who are active and engaged.

This means that you’ll be sending emails to subscribers who are genuinely interested in your business offers. And, these subscribers will be more likely to open and read your emails, click on your offer links, and make a purchase or book your services.

5. Improves email campaign reporting accuracy

If your email list contains inactive, invalid, and unengaged subscribers, it skews your email marketing statistics report. With email scrubbing, you can get accurate data based insights into the success (or failure) of your email marketing campaigns.

Imagine you have 1000 subscribers, 200 of which are inactive, invalid, or unengaged. And, your report showed that only 250 opened your email. You would calculate the open rate as 25%.

However, when you remove the 200 subscribers from your list, your report will reflect the actual result of your email campaign. That is, 250 out of 800 subscribers opened your email, resulting in an open rate of 31.25% – a significant difference.

6. Reduces your carbon footprint

Surprising! But yes, email scrubbing can reduce your carbon footprint. When you clean your email list, you’ll be left with fewer, though, quality subscribers. This reduces the email addresses you’ll have saved in email servers and databases. Thus, you’ll contribute to reducing the overall energy consumption needed to keep the servers running!

Now you know some of the benefits of email scrubbing and a clean list, let's look at some of the warning signs that indicate it may be time to start email scrubbing!

How often should you scrub your email list?

Email scrubbing isn’t a one-time task. You have to do it regularly to maintain a clean and healthy email list. Here are some signs to look out for to know when you need to clean your email list.

1. Email bounce rate is increasing

Bounce rate is the percentage of emails that bounce back. There are two types. Hard bounce, which occurs when you send an email to a nonexistent domain or email address. And soft bounce, which occurs when you send emails to a full inbox.

If you notice your emails are reaching a dead end and bouncing back, it’s time to scrub your mailing list for inactive and invalid email addresses. You should also look out for email addresses with misspellings or typos.

2. Unsubscribes from your email lists are increasing

Unsubscribes are not a bad thing. And, your emails should always include an unsubscribe link so that people who are no longer interested in your emails can easily stop receiving them.

However, increasing unsubscribes is a sign that your offer or content no longer resonates with your subscribers. And, it's better to identify and remove those people before they do so themselves, or worse hit “report spam.”

If you've recently changed your business or content focus, you should do a bit of email scrubbing. One way to do this is to send an email asking subscribers who haven’t been engaging with your emails or shown interest in your new focus area to feel free to opt out.

3. Spam complaints are increasing

Contacts often mark emails as spam when they're no longer interested in your emails. For some, it's easier to make these spam complaints than scrolling to the bottom to find the unsubscribe button! And, this is why I always recommend including an add-list unsubscribe option in email headers.

Unsubscribe in email header

Also, subscribers may mark your email as spam because they don’t remember subscribing to your list. Or, just because they think your emails are too frequent. Or, your offer is no longer relevant to them.

In any case, when you notice a spike in spam complaints, then it's time to scrub your list clean. Spam complaints are red flags that cause ESPs and ISPs to start treating all of your emails as spam.

So, remove all inactive and unengaged subscribers from your list. Take action before the spam reports lead to your domain being blacklisted and all your emails to all your subscribers are delivered to the spam folder.

4. Open and click through rates are decreasing

When subscribers aren't opening your marketing emails, let alone clicking through to purchase your offers, it's a sign that they aren't interested in receiving your emails anymore. And, perhaps they are just too lazy to click the unsubscribe button.

Of course, the problem might be your email subject line, copy, or design. Or, even the time you’re sending the emails. However, if your open and click through rates are decreasing, you should consider email scrubbing.

At the very least, scrubbing your list will help you get better insights into your email campaigns. And, it’ll remove uninterested subscribers who may end up hitting the unsubscribe or “report spam” button.

In summary and to answer the question, “How often should you scrub your list?”

There's no “set-in-stone” number of times to scrub your email list clean. You have to be vigilant to the signs that your list needs scrubbing, although you don’t have to wait for the signs. I recommend scrubbing your email list every 3 months, or at least twice a year to maintain good email list hygiene.

How to scrub your email list

Now that you know why and when to clean your email list, let's explore the how. The specific process of scrubbing your email list varies for different ESPs or email scrubbing services. Nevertheless, here are the general steps for email list scrubbing.

Step #1: Decide which email list to scrub

If you're like us at EmailTooltester, you have multiple email lists. For instance, you may have a list of newsletter subscribers you acquired via your website sign-up form and another you acquired via a lead magnet campaign.

If yes, you should first decide which email list needs scrubbing first. Making this decision can be based on information such as the list age, activity, or size. However, all lists should be scrubbed periodically, no matter how old, active, or large.

Personally, I'll suggest first scrubbing your oldest email list. A list started years ago will probably have more inactive contacts and invalid emails than one started a couple of months ago, especially if the list hasn’t been cleaned for years.

Step #2: Remove duplicate, miss-spelled, spam and fake email addresses

Before you go after inactive subscribers, first get rid of duplicate, fake and spam email addresses. And, identify and correct misspelled email addresses.

You may have duplicate emails because a subscriber unknowingly resubscribed to your list. Unfortunately, there’s no way to prevent prospects who are already subscribers from resubscribing. So, you’ll have to check and remove these duplicates manually or with an email scrubbing tool or email verification service.

Also, find email addresses with random combinations of letters and numbers. These are examples of spam email addresses that you should remove from your list. Disposable and temporary emails should also be removed.

As for misspelled emails, subscribers sometimes make mistakes when entering their email addresses. For instance, instead of, they submit These spelling errors can be identified and fixed easily.

Step #3: Define what constitutes an inactive subscriber

Before taking action on inactive subscribers, you have to first define what classifies a subscriber as inactive to you. Is it a subscriber who hasn't opened your emails in 90 days or 6 months? Or, one who opens your emails but has never clicked through on your offer?

The definition of an inactive subscriber differs from business to business. Your email send frequency also matters. For instance, if you send one email per month (not recommended), then someone who hasn’t engaged in 3 months isn’t really inactive. They probably don’t remember you.

If you send emails at least once a week, a good way to identify inactive subscribers is to tag those who haven’t engaged in 3 months as inactive. And, this is great timing if you scrub your email list clean every 3 months!

Step #4: Segment inactive subscribers

Next, use your definition of inactive subscribers to segment them out of your main email list. You can do this automatically with your email marketing software and have these subscribers grouped together in an inactive subscriber list.

However, not all inactive subscribers are the same. A subscriber who hasn't opened your email in a year is different from one who hasn't opened in 3 months. And, one who opens but hasn’t clicked through in 6 months is different from the other two.

Thus, you should further segment the inactive subscriber list based on their behavior (open and click through rate etc). This will help you with creating targeted re-engagement campaigns, which is the next step.

Step #5: Try a re-engagement campaign

Before you say that final goodbye to all the email addresses on your list that are inactive, give your relationship with your subscribers another shot. You should try to win them back with re-engagement campaigns.

A re-engagement campaign involves sending an email (or series of emails) to reconnect with inactive subscribers and get them to re engage. While offering an incentive such as a free offer or discount is a good idea and works, it isn’t the only way.

You can send a “checking in, are you still there” email like the Typeform email below. Or, a friendly reminder email reminding them of why they got on your list. Or, a personalized recommendation email to entice them to re-engage.

Re-engagement email campaign

Step #6: Unsubscribe inactive subscribers

Finally, you can remove inactive users from your list if they don’t respond to your re-engagement emails. And, you don’t have to spend time and effort doing it manually, one by one. Imagine having to click unsubscribe for each of 500+ subscribers!

Instead, your ESP (or email scrubbing tool) can help you with this. All you have to do is filter your list to show the inactive subscribers that are to be unsubscribed. For instance, your filter condition can be something like:

  • Didn’t open emails in the last 3 months
  • Didn’t open the re-engagement email

Once you have filtered the email list is this way, you can usually just click one button in your ESP (or email scrubbing service) to automatically remove all those inactive subscribers from your list.

Tips For Keeping Your Email List Clean

Keeping your email list clean isn't just about email scrubbing. You have to take proactive steps to maintain a clean mailing list. Here are some tips.

  • This goes without saying, but NEVER buy an email list. They are always choked full of inactive, invalid, and spam email addresses. And, it would only get your domain blacklisted with the email service providers.
  • Use double opt-in for signups to ensure that only contacts who are truly interested in your business join your mailing list. And to validate that the email address is real.
  • Always segment your email list and personalize your emails based on subscribers’ behaviors, interests, and preferences in order to send targeted emails that interest each subscriber.
  • Send preference defining emails for marketing campaigns that may overwhelm subscribers. For instance, letting them choose whether they want to receive Black Friday offers.
  • Add an unsubscribe button to every email. And, not just at the bottom either. Add the button in the header of your email, so contacts can hit unsubscribe rather than spam.

Scrubbing Email Lists is a vital part of your Email Marketing Strategy

If you've never scrubbed your email list, you’re hurting your email marketing efforts. Many of your emails won’t be reaching your subscribers, let alone converting. And worse, more spam complaints may lead to you getting blacklisted by email providers.

Scrubbing your email list is crucial to your email marketing success. This means removing inactive, invalid, and unengaged contacts from your databse (once you've tried to re engage subscribers), to ensure that your emails are reaching those who are genuinely interested in your business.

So, take the time to scrub your list, at least twice a year. There are plenty of specialized email list cleaning services that can help you with this. Think of it as a digital cleanse that keeps your email list clean and healthy, with quality subscribers who engage and convert.

Get started with the email scrubbing steps outlined in this post, and feel free to ask for help in the comment section.

The authors

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Cai Ellis

SEO Manager

Hi! My name is Cai, and I've worked in digital marketing for many years. More recently, I've been concentrating on email marketing, through testing tools and writing guides. And I've also picked up a bit of SEO know-how along the way! If you've got questions about these or any related subjects, I'll be happy to help!

Robert Brandl

Founder and CEO

Hello! I'm Robert, an email marketing expert with over 15 years of experience in the industry. After honing my skills by serving major corporations working for an agency, I founded EmailTooltester as a passion project to help small and medium-sized businesses. My goal is to assist you in maximizing email marketing's potential.

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This article has been written and researched following our EmailTooltester methodology.

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