Also known as email scrubbing, email hygiene is the single most important aspect of email list management.

If you have a large email list already, you may find that you:

  • Can’t personalize emails due to lack of information.
  • Don’t have leads and customers well organized in your list.
  • Get complaints from sales that data is inaccurate.
  • Have heard great things about email marketing ROI but don’t have the same results for your list.

You can improve the subject lines, collect more emails, send more emails, but none of those things matter if you don’t have a clean list.

You can’t personalize emails without accurate data. Personalized emails generate six times higher transaction rates than generic ones. So that might be why you aren’t seeing the ROI everyone’s talking about.

In this article, we’re going to cover the nitty-gritty of email hygiene and how to get your list sparkling clean.

Curious about the current state of your email list? Request a free data quality check.

Get a sparkling clean list with this 15-point email hygiene checklist

Email hygiene refers to keeping your list accurate and up-to-date

Your email list management efforts won’t be effective without a clean list.

More than 20% of email sign-ups contain typos, syntax, domain, and other errors (source). 

This is the #1 most important aspect of personalized email marketing. A segmented list, high open and CTR rates, and extraordinary email revenue all start with a clean list.

Email hygiene is defined as the regular process of verifying and removing invalid email addresses from your list.

But it’s more than that.

Valid email addresses aren't quite enough. You also need data that is in the right field, no duplicate contacts and integration across your lists.

Want to test the quality of your email list? Get in touch for a free data quality check—it only takes a few minutes!

What is email data cleaning?

Data is like oil.

For one, it’s the most valuable resource businesses have today.

Back in oil’s glory days, you’d take the crude oil and clean it and process it to turn it into petroleum, paraffin, diesel fuel, or another final product.

You wouldn’t just keep the crude oil and cash checks.

Data is similar, except even more precious. You can sell crude oil, but you can’t do anything with inaccurate data.

Data cleaning or data cleansing is removing or correcting data that is incorrect, incomplete, irrelevant, duplicated, or improperly formatted. It’s fixing all the data that means nothing to your business.

Email hygiene best practices: how to normalize data

Let’s say you have all of your data in an Excel sheet.

The columns are categories, and the rows are the information you have about a specific person.

There are two ways to look at it, and it should be normalized across both:

  • Horizontal consistency
  • Vertical consistency

Horizontal consistency in your email list data

The horizontal approach is everything you have about one person.

We’d refer to this as internal consistency: does all the information you have about this contact make sense?

 horizontal data consistency in email list hygiene

Horizontal data consistency

For instance, if you have a contact with the name Markus Beck and the email is, that’s a red flag. 

Additionally, if the email is listed as and then the company is listed as Ziemens, then that’s also a horizontal inconsistency.

Does Markus work for two companies?

Does he only work at one? If so, which?

As you go through your contact rows, each person is going to be a whole new page, a whole new picture. Making sure you have the right information about each contact is the first step in having a clean email list.

Email list hygiene: vertical consistency

This is when you look at the data of your list as a whole.

Are there only email addresses in the email field?

vertical data consistency in email list hygiene

Vertical data consistency

Are all the first names really in the first name column, or are they somewhere else, for some reason?

So you also have to look at all entries, one at a time. But you also need to check one column type. 

You're looking at inconsistencies within this one column type. 

And then you're trying to find out whether any sorts of patterns arise.

Maybe for 20% of your entries, the street name is in the city name, the last name is in the country name field, and the country name is in the phone number field. That means your subjects are hitting tab too many times, 20% of the time.

The question you can ask yourself here is: where do these errors come from and how can they be corrected in bulk? 

So we’ve covered the basics of email list cleaning, but there also are more complex cases.

Email hygiene: correcting complex duplicates

Duplicates are when there are several entries in your database for the same person.

In other words, you have Tim Jones and Timothy Jones (same person) that may be segmented into different groups because your list isn’t clean.

Maybe it’s one email address with two names: as Tim Jones and Timothy Jones.

Sometimes it’s even two different names, two different emails, but the person is the same:, Tim Jones, and, Timothy Jones.

You’d then be sending him two emails, only one is targeted - and he might not open the right one.

That’s a simple duplicate. Maybe his email is in there 2-3 times, and with a few minutes of research, you realize it’s the same person and you can merge the contact.

So if Tim Jones had a complex duplicate in your database, things get even trickier.

Maybe you have three data entries:

  1. Tim Jones,, (909) 555-6456, Austin
  2. T. Jones,, (909) 555-6456, New York
  3. T. Jones,, Barcelona

So to what extent do we know these 3 entries are the same person? There are indicators that tie them together: the same phone number, same first initial and last name. But the domain names are all different, the cities are different. 

But they may not be the same person. This is where things get complicated in email hygiene.

Curious about the current state of your email list? Request a free data quality check.

Email list cleaning: people who never engage with you

Even if every contact in your list is complete and accurate, there’s always that person that just isn’t interested in your emails.

That contact who has never opened a single email you’ve sent, and never will.

Maybe it’s all gone to a folder they never look at, or maybe they genuinely don’t care.

It’s important to regularly remove these people from your list. It hurts your metrics and makes no sense to try to engage with people who aren’t interested.

We recommend using your email marketing provider to tag people who haven’t opened an email in 90 days. Every 90 days, send an automated re-engagement campaign. Those who open it can move back to your regular list, and those who don’t get binned.

B2B data hygiene: managing leads the right way

Without all the information above being clear, organized and accurate, how can you manage these leads?

Conducting a lead generation program without first investing in clean data wastes 27.3% of each sales rep’s time, or 546 hours on average a year per rep (source).

How many reps do you have?

If you pay your sales rep the average US salary of $33/hour, and you have 3 sales reps, that’s  $54,054 spent for absolutely no reason. We’re also not counting the losses in potential business.

Enough theory. Now let’s look at how you can improve your email hygiene and data quality.

Email lead hygiene: Warning signs you should improve data quality

We recommend making email hygiene a regular practice in your business. However, there are some warning signs to indicate that your email data quality is going from bad to worse.

email list metrics

Low open rates

For context, average email open rates are 21.33%.

When your open rates start to plummet, that can signal a few things.

Low open rates might be tied to low deliverability rates. If few people are receiving your emails, they can’t open it. 

It could also mean your subject lines aren’t well written, or that your email list isn’t well segmented and your message doesn’t resonate with anyone (too generic = not targeted). Here we discuss the basics of email list segmentation and what you need to get started.

It could also mean you’re sending too many or too few emails. In any case, an open rate that suddenly falls is a strong indicator of a dirty list.

Low click-through-rates

A click-through rate (CTR) is the percentage of people who have opened your email and then clicked on the link you provide inside.

This indicates that people find the content of your email useful. 

If you have a low CTR, that generally means people aren’t interested in what you have to offer. For the record, the overall average CTR across industries, according to MailChimp, is 2.5%. 

If it’s way lower, the main way to fix this is by segmenting your list better. As in, sending more specific emails to a smaller subset of people.

If you have a sudden drop in CTR, that means something strange is happening with your list. This is an indicator you need to clean it.

High bounce rate

Imagine you take 100 emails, print them out, crumple them into balls and throw them at a box. An inbox, if you will.

20 of those paper balls hit the edge and bounce off, never making it inside.

This is a 20% bounce rate, the rate at which your emails never make it inside the intended inbox. This example would mean you have terrible aim - the average bounce rate (combining both hard and soft bounces) is less than 1%. 

If your bounce rate starts to go above the 2% mark, it means you have an email deliverability problem. It means that the emails you have are incorrect.

This isn’t only an issue because your subscribers aren’t receiving your emails, but high bounce rates damage your sender reputation. It means email providers like Google and Hotmail can see your bounce rates and start to assume you’re sending spam.

A high bounce rate means you need to clean your email list.

Related Post: How to Reduce Your Email Bounce Rate to Below 1%

Emails are going to spam

If your emails do start going to spam, that’s another indicator you need to clean your list.

You can check your IP reputation on websites like Talos or Watchguard’s IP lookup page.

If you have a spammy reputation, the first thing you should run to is cleaning your list.

Related Post: How To Send Bulk Emails Without Spamming

Data hygiene in email marketing: How often should I clean my email list?

Ideally, your list should always be clean. That’s hard to maintain - considering B2B email data decays at 2.1% per month (22.5% per year).

Imagine your email list is a home. A huge company would be a household with a lot of kids. Things get messy quickly, and you need to clean more regularly to have some kind of semblance of a livable house.

A small company or a solopreneur is like a single person, living alone, who’s at work most of the day. You need to clean a lot less frequently to keep your house decent.

You should clean your list based on the size of your company and the above indicators. If you’re an SMB, we recommend cleaning your list once a month or more, preferably with a tool or partner that does it for you.

Best email list cleaning service

This all depends on the size of your company and your needs.

We wrote a guide for choosing the best data quality tool.

In any case, the most important thing to pay attention to is who in your company uses data and what your tech stack is.

If you’re going to invest in a data cleansing tool for your email list, you might as well get one that can also merge this cleaning with your sales team’s CRM or the ERP.

You can’t just clean your email list and leave data in other databases dirty. Here at tye, we clean your data so you don’t have to, right in your own systems.

Curious about the current state of your email list? Request a free data quality check.

Clean your email list with this 15-point email hygiene checklist

Markus Beck

Markus Beck - November 15, 2020

CEO with a passion for data relationships. Markus is half Finnish, half Austrian & fully committed to helping businesses keep bad data from ruining great relationships. Process Engineer by training, with digital marketing & project management skills from previous jobs.