Email cleaning supplies

List Hygiene and the Importance of Email Validations

Does your email list spark joy? Would Marie Condo approve of how you’ve been managing your contacts? Or, is it kind of a cluttered mess?

After a while, your email list loses that “new car smell.” That’s why it’s important to freshen things up with email list hygiene (aka email list scrubbing). Maintaining a clean email list is an important process that supports email deliverability and ensures you’re accurately measuring email engagement.

But if you’re the kind of person who asked “Why?” when your parents told you to clean up your room (as most of us were), you may also procrastinate a bit when it comes to a clean email list.

So, is your email list clean and pristine? Or is it clogged up with invalid emails and starting to smell? Let’s take a look at email list health, why it matters, and how to keep your list in good shape using the right tools and processes.

What is email list hygiene?

Email list hygiene or email list cleaning is the process of “scrubbing” your contact list to remove invalid and outdated addresses, duplicate email addresses, as well as inactive and unengaged subscribers.

A healthy email list has several characteristics:

  • All or nearly all of the email addresses are real/verified
  • Nearly every email gets delivered to the inbox
  • Your subscribers are highly engaged with your content
  • Your list produces a return on investment, in whatever form that takes for you

Over time, if you neglect email list management, these characteristics begin to wither.

Email lists can decay every year by up to 22.5%. Life happens, people move, change jobs, forget to unsubscribe, and some use auto-delete. While these subscribers are the most obvious cause of poor list performance, there are multiple variables that impact the health of an email list and hurt deliverability. 

Some email addresses that were abandoned become spam traps, and if you keep sending emails to those addresses, your sender reputation could become tarnished. That means you are more likely to land in the spam folder.

Other subscribers stay with you, but they lose their previous enthusiasm over hearing from you. Engagement declines. Inactivity increases. 

Six signs that your email list needs cleaning

If you’ve never cleaned your email list, then it needs to be cleaned. It’s that simple. If you’re suffering from poor deliverability, a cleaning may be a good first step to take as well. 

There are lots of ways to measure list health. Here are some of the most important ways to tell that you need an email scrubbing: 

1. The list contains purchased contacts

Hopefully, you already know what a bad idea this is. Purchasing an email list is one of the fastest ways to get blocked. That’s because they often contain spam traps used for the express purpose of catching people who pay for email contacts.

Still, you may have inherited an email list after an acquisition or starting a new job. How do you know if the contacts in your email database were legitimately and legally acquired? If you aren’t sure, you could be in violation of data privacy laws like GDPR, which requires an opt-in for commercial emails. 

The safest thing, in this case, is to do some list cleaning using a tool such as Mailgun Optimize’s Email Validations. We’ll tell you more about ways to use an email verification service later.

2. Rising bounce rates

A clean email list should be able to keep bounce rates under 1%, in most cases. While soft bounces usually indicate a temporary problem like a full mailbox, hard bounces are a sign that you’ve got invalid addresses on your list. 

Either type of email bounce could point to a contact that should be removed during email list cleaning. But hard bounces could indicate more serious issues, such as recycled spam traps and typo spam traps. If you don’t remove these contacts, it will eventually hurt email deliverability. 

They’re useless contacts anyway. So get rid of them. Keep them around is like keeping 

3. Spam complaints

If people are marking your emails as spam, there’s no reason to keep them on your list. 

It’s a clear sign that they don’t want to hear from you. Now, maybe they did sign up and you’re not spamming them at all. Sometimes people forget when they’ve subscribed. Maybe they just want to unsubscribe and mark messages as spam instead. A spam complaint isn’t necessarily your fault. But failing to remove contacts who make spam complaints is a mistake.

The spam complaint rate is a major signal to the mailbox providers like Gmail, Outlook, and Yahoo Mail. They judge your sender reputation and decide whether to send you to the inbox of the junk mail folder. 

An increase in your spam complaint rate means some email list cleaning is a smart move.

4. High unsubscribe rates

This is another sign your email subscribers no longer see your content as relevant, or just don’t want to hear from you anymore. Some email list churn is inevitable. People come and go. 

The point here is that, if your unsubscribe rate is high, there are probably too many old contacts on your list who no longer want to receive your emails. Rather than unsubscribing, plenty of inactive contacts just ignore your messages. So, rather than waiting for them to finally cut ties with your email marketing, email list cleaning takes a proactive approach.

Remove contacts who’ll likely unsubscribe anyway, and get rid of the  “dead weight” so you can keep a clean email list. But the big question is how do you identify those subscribers so they can be removed? That’s when you need to look at email engagement metrics.

5. Waning email engagement

Any engagement at all indicates a valid and active email subscriber has received your email. You can measure engagement with open rates, click-through rates, conversion rates, and more. All of these metrics indicate actual people are opening, reading, and responding to your emails in some way. Read, skim/glance, and delete metrics can also be informative. 

However, an email list that needs cleaning will have subscribers who haven’t opened or clicked on anything in months (if not longer). Those who immediately delete your messages are doing your marketing efforts any favors either.

Very low engagement metrics indicate an uninterested subscriber base. This can happen even if you’ve been diligent to clean up the list by purging bad email addresses. If your ‘good’ email addresses aren’t responding to anything you’re sending, your list is still unhealthy. 

6. List growth rate

If your email list is getting smaller, that means you’re losing more people to unsubscribes than you’re adding. That could be an indication that something isn’t working with your email marketing campaigns or list management. 

On the other hand, if your list is growing at a high rate, that too could be a sign your list needs cleaning. Let’s say you just held a virtual event, attended a conference where you collected contacts or launched a report that generated a bunch of leads. When there’s a spike in the size of your list, there’s also a good chance you picked up some bad emails that should be cleaned.

Six ways to maintain clean email lists

With all this in mind, let’s look at six ways to keep your email list clean and your list health strong.

1. Keep subscribers engaged

This should begin the moment someone subscribes to your email list. Send a welcome email campaign to kick off the new subscriber relationship. A series is better than a single email for several reasons: 

First, a single email might get overlooked. Second, multiple emails give you space to make different types of offers for engagement. Offers may include helpful articles to read, white papers, quizzes, free trials, discount offers, and sales appointments. Third, multiple emails allow you to tell your brand story in bite-size segments. Fourth, you’ll be able to touch on different benefits to the subscriber. 

A welcome email can also set expectations around how many emails the subscriber can expect and what kind of content they’ll receive. 

2. Segment your email list

Organization is a big part of cleaning. And when it comes to a clean email list organization = segmentation. 

Email list segmentation also boosts engagement, because you’ll be sending more relevant emails to your subscribers. This keeps them feeling positive about getting your emails and lengthens the time you’ll be in their good graces.

Segmentation also makes email list maintenance easier than managing a gigantic bulk email list. Each email sent deals with a smaller subset of subscribers, so spotting and dealing with any problems takes less effort. If you create a segment with subscribers who’ve engaged in the relatively recent past, those who fall outside of this segment can already be flagged for inactivity so you can keep a closer eye on them.

That doesn’t mean you should remove them just yet. Instead, use the next suggestion.

3. Send re-engagement campaigns

With a segment of subscribers who haven’t engaged for a while, create a re-engagement campaign specifically for them. Make it clear in your subject lines with phrases like “We miss you” and “We want you back.” Include sweeteners like a special discount.

This is part of cleaning your list because it will further isolate the truly inactive email addresses from ones who just haven’t been paying you as much attention. Any subscribers who take zero action on the entire re-engagement series are probably never going to re-engage.

4. Remove inactive subscribers

After a lengthy period of inactivity (and a cold shoulder response to your re-engagement emails), it’s safe to assume these subscribers have either changed email addresses, or your content no longer sparks joy for them.

You can now proactively unsubscribe those addresses. Yes, this means you are willfully shrinking your email list. But these are bad leads, dead leads, or abandoned email addresses, and they’re doing zero good by remaining on your list. If you let them stay, they’ll only damage your sender reputation at best, or become spam traps at worst.

It may feel painful to delete once-promising leads, but practicing email list cleaning like this will result in a better sender reputation, improved email metrics, and higher deliverability rates. 

5. Delete invalid email addresses

Sometimes people use fake email addresses or “burner email addresses,” which are disposable email addresses. Other times, people make typos when entering their contact information. A double-opt in can help keep these invalid emails off your list. But some invalid email addresses are inevitable and will need to be cleaned up.

Email Validation from Mailgun Optimize makes this super easy. Simply take all the email addresses that didn’t respond to the campaign, put them in their own spreadsheet or CSV, and our verification tool can check to see which ones are invalid. 

6. Verify email addresses from the start

A robust email validation tool like Mailgun Optimize also conducts email validation right when the person subscribes. We’re talking about real-time email verification here.

This is super helpful, and not just to stop all the bots and spammers. People also make typos, and a verification tool will catch this right away so your welcome email series doesn’t go to a non-existent email address and needlessly damage your sender reputation and deliverability rates.

Get Mailgun Optimize and keep clean email lists

Email lists require constant maintenance, but keeping your list clean and healthy will help you get closer to achieving the maximum ROI from your email marketing program. Using Email Validation as a list cleaning tool is actually just one of many features of Mailgun Optimize’s email deliverability suite.

You can also use our email deliverability suite to:

  • Monitor inbox placement
  • Find out if you’re on a blocklist and get help with the removal
  • Find out if you’re sending to any spam traps – before you send out your next email
  • Preview how your emails will look on dozens of devices, including in dark mode

Learn more about Mailgun Optimize and explore the other email marketing tools we have to offer. Find out how Email on Acid and Mailgun Optimize help you deliver email perfection.

This article was updated on September 19, 2022. It was also updated in April 2020 and was originally published in April 2015.


When was the last time you cleaned up your database of contacts? Sometimes senders forget about conducting email list hygiene, and that can cause serious deliverability problems. Use List Validation from Mailgun Validate to easily verify your entire list before the next big campaign. Lower your bounce rates, improve email engagement, and maximize email ROI.