---

If it doesn’t spark joy, let it go. We all know it’s good practice to reduce clutter in our personal life – why not do the same for your email marketing program?

We’ve all been there and know that achieving good open, click-through, and delivery rates is a balancing act. Many areas make up good email deliverability, and one of the most important is mailing list hygiene. 

Let’s break down everything you need to know about email list cleaning – the what, why, when, and how – so you can quickly be on your way to a cleaner list.

Email list verification vs. email list cleaning

Email list verification and email list cleaning are very similar but not quite the same. Email verification services determine if the emails on your list are valid, but they don’t necessarily tell you if a real human customer is behind a given email address.

Consider this, for example. As a marketer, you’ve set up a verification and validation service to identify if the emails on your lists are valid or invalid. However, don’t forget that spam traps, bots, and other emails can pass verification because they open emails and click through just like real users with real emails.

On the other hand, complainers or screamers are real people who report you to internet service providers (ISPs), the Federal Trade Commission (FTC), or blocklists. These are real people behind real emails who are possibly reporting you and causing you massive issues. Because these are real people with valid emails, they can slip by a verification test. 

Email list verification can inform the list cleaning process, but you’ll still need to do some scrubbing. List cleaning goes a step further. It involves the process of removing inactive or unengaged users from your mailing list.

Why should I clean my email list?

We briefly touched on why email list cleaning is important, but here are eight specific reasons why:

1. Your data has changed.
2. Your forms aren’t protected.
3. You’ve received spam complaints.
4. You want to improve your email deliverability and sender reputation.
5. You’ve inherited a list in your new role.
6. You’ve purchased an email list.
7. You want to avoid spam traps.
8. You want to avoid landing on an email blocklist.

Let’s go over each of these in detail.

1. Your data has changed.

The average mailing list depreciates by about 30% a year because people switch mailbox service providers, change jobs, and abandon old email addresses. Remember, quality matters more than quantity.

Cleaning your list regularly to keep your spam complaints, bounce rates, and unsubscribes down. At the same time, keep your deliverability, click-through, and open rates high.

2. Your forms aren’t protected.

You’ve probably got an entire team taking care of your business’s cybersecurity issues, but if you have an unprotected input form, you might be in a bit of a bind.

To ensure that you’re only getting real leads or subscribers through your web forms rather than bots, spam traps, or typos, you need to put a real-time email cleansing API into place. This will not only help decrease the fraudulent or inaccurate data attacking your forms, but it will also protect your deliverability and sender reputation. Most importantly, cleaning your mailing list will improve your campaign ROI and create a better customer experience. 

3. You’ve received spam complaints.

Uh-oh! This can be a nasty one. One reason why you should clear your lists is to avoid spam complaints. If your audience doesn’t like your emails and doesn’t see an obvious unsubscribe button, they might report you as spam. This, in turn, leads inbox service providers (ISPs) to think of your emails as spam and to place them in your subscribers’ spam folders instead of their inboxes. Keep your mailing list up to date to drop disenchanted subscribers who might view your messages as spam. Fewer spam complaints mean fewer deliverability issues.

4. You want to improve your email deliverability and sender reputation.

A disengaged list results in poor email deliverability and a failing sender reputation. Basically, there’s a whole host of issues and headaches if you do not keep up with your email list scrubbing.

Management Service Providers (MSPs) like Gmail can punish you for poor list hygiene if you send irrelevant content to your users who haven’t opted in or aren’t engaged. 

5. You’ve inherited a list in your new role.

We’ve all been there once or twice. You’ve entered a new job, and you’re left with an email list you don’t know much about. There are so many questions that you may not have the answers to, like “how did these emails come to the list?” “Are they purchased?” “When was the last time the list was cleaned?” “Is this a bulk email list with disengaged subscribers?”

The best way to answer these questions is to clean your list and determine what is good and bad before you send. 

6. You’ve purchased an email list.

You should never buy an email list. In email marketing, quality always comes before quantity. It’s best to build your list organically, but if you have been guilty of purchasing lists or inherited one, cleaning is necessary. 

The truth is you have no idea what type of emails are on those lists that could potentially ruin your deliverability and sender reputation and permanently block you from sending. 

7. You want to avoid spam traps.

One important reason you need to clean your mailing lists is to identify spam traps. As we mentioned above, they aren’t easy to see because these traps open and click like real email addresses.

Email validation alone isn’t enough to truly clean your mailing lists. After all, email verification will tell you if your emails are valid or invalid. Verification alone can’t tell you if your mailing list has bots or spam traps.

8. You want to avoid landing on an email blocklist.

If a major blocklist sees spam being sent from your IP or domain, your emails can be blocked, and you could be delisted. The delisting process takes a few days or weeks, but your IP or domain will continue to be blocked until that process has been resolved. It’s a whole task you should avoid.

When should I clean my email lists?

Okay, so now you know why you should clean your mailing list. But when should you do it?

Here are some guidelines for when you should clean your email list:

1. You’re transferring data between Customer Relationship Management (CRM) tools.
2. You’re switching email service providers (ESPs).
3. You’re adding or switching to a customer data platform (CDP).
4. You’ve acquired new emails.
5. You’re running a re-engagement campaign.

1. You’re transferring data between CRMs.

Having bad CRM data can negatively affect your marketing campaigns’ ROI, kill sales productivity, and waste money. According to Gartner, “Organizations lose $13.3 Million yearly on average on poor data.”

2. You’re switching ESPs.

The same process goes for switching from one ESP to another: clean your data! You’ll want to separate active from inactive subscribers. This allows you to create a reactivation campaign at your current ESP.

3. You’re adding or switching to a CDP.

Before you gather your data with a CDP, you’ll want to ensure that you maintain updated and accurate data. Whether you’re new to your role and inheriting a bunch of data sources that need to be organized, or you’re ready to discover new segments, build models, and deliver real-time personalization, cleaning your list should be high up on your to-do list.

4. You’ve acquired new emails.

Anytime you gather new email addresses, it’s crucial to make sure they are legitimate. This helps you avoid any issues down the road. 

5. You’re running a re-engagement campaign.

Before you start sending out your “we miss you” emails to your inactive email subscribers, clean your list to help you weed out spam traps and other threats. 

How often should I clean my lists?

In a perfect world, your email lists should always be in tip-top shape, but we all know it’s not that easy. We recommend cleaning your lists every quarter. Like spring cleaning, changing your clothes depending on the season, or cleaning up the leaves before the winter months, you should remember to clean your lists regularly and often. 

Implementing real-time verification in your web forms is just another small way to help protect your forms from fraudulent addresses daily. 

How can I scrub my email list?

Now that we’ve gone over the basics of mailing list hygiene, let’s walk through a step-by-step process to clean your mailing list.

1. Run an email list verification to separate valid addresses from invalid addresses.
2. Clean up duplicate email addresses.
3. Identify disengaged subscribers. This can be based on the amount of time they’ve been inactive or based on multiple hard bounces.
4. Try to re-engage inactive subscribers.
5. Based on your findings, segment your list and remove inactive subscribers.

What are the best email list cleaning services?

Not quite ready to tackle email list hygiene on your own? At Email on Acid, we provide an email verification service, but we also recommend that you take a look at these list-cleaning tools:

• Webbula is a comprehensive email hygiene service that provides list verification and list-scrubbing services.
• InboxReady by Sinch provides email verification solutions for both new contacts and your existing list of subscribers. Validate email addresses at signup or clean your list.
• Xverify employs automation features and an email checker to make sure the emails on your mailing list are deliverable. Xverify also removes invalid data that’s entered in its interface.
• QuickEmailVerification verifies contact lists imported from your ESP, computer, or via the API and provides automated list cleaning services. It also performs real-time validation of incoming emails incoming from online forms. 

What are some best practices to maintain mailing list hygiene?

We’ve gone over why, when, how often, and how to clean your mailing list above. However, the best course of action is preemptive. Check out the following best practices to maintain a clean email list at all times:

Use double opt-ins: Always make sure your subscribers are actually human beings opting into your mailing list by using double opt-ins. This also helps limit the number of human error typos in your mailing list.

Provide an “opt down” option: Instead of just providing an opt-out option, provide an “opt down” so your subscribers can choose to stay engaged – just not as engaged as before. In other words, this means your user can choose to receive fewer communications from you – say once a month instead of once a week. Or, they can choose to keep receiving your quarterly email newsletters but not every single promotion or new product announcement. This keeps your subscribers happy and also helps email marketers to segment their mailing list to send appropriate email campaigns.

Send a re-engagement email campaign: Subscribers falling into radio silence? Try sending a re-engagement email campaign to invite them to engage once more. You can use this as an opportunity to prune your mailing list based on your subscribers’ responses.

Use marketing automation: Marketing automation is a great way to scrub your email list and purge invalid, disengaged, or outdated email addresses. Simply set up rules to automatically segment or remove customers who haven’t engaged for a set time limit or whose addresses have bounced twice or more. This is a great way to reduce email bounces and improve your sender reputation.

Grow an organic list: As we mentioned above, never purchase a list. Growing a list organically might take time, but it will pay off in the long run as you maintain a higher customer engagement rate and retain your conversions.

Wrapping up

If you’re stuck not knowing where or when to start cleaning your mailing list, we hope this article gives you some guidance on where to start and what solution is best for you. Check out InboxReady by Sinch to learn more about how email verification can help and discover other industry-leading email deliverability solutions.

Make email list cleaning a priority. Many people have changed jobs, and companies closed in the wake of the COVID-19 pandemic. Data hygiene is one of 10 action items Email on Acid recommends in the special report, Email Marketing and the Next Normal.

This article was updated on July 28, 2022. Our friends at Webbula contributed to the content in this piece, which was first published in January of 2021.