How to Clean an Email List (and Keep it Clean)


What makes a “clean” email list? And how do you go about cleaning a list that isn’t clean? Let’s talk about email hygiene: You want to set your account up for success in the ideal structure for your email marketing tool, or you can update your account following our guide. But even with an organized account structure, faulty or disengaged emails can be added to your list. This can ultimately lower your engagement metrics like open and click-through rates. This can in turn affect your email deliverability, leaving you to fall in spam filters.
In this guide, we’ll walk through what it means to have an “unclean” email list, how to know if your account has a problem, and how to clean it to optimize your nonprofit email marketing strategy.
How to Marie Kondo your email list: Discard all email addresses that spark bounce. Click To Tweet

Unclean List Indicators: Bounces and Low Open Rates

Below are the 2 main indicators of an unclean email list: Bounce rate and low open rates.

Bounce Rate

An email bounces when it’s not able to be delivered to a subscriber’s inbox. It could be due to their inbox being full, the email address being wrong, or any other number of issues. A bounce rate is the number of bounces divided by the number of people the email was sent to. Most EMPs (email marketing providers) will clean an account of bounces. Still, you should keep an eye on the rate to make sure there isn’t a technical issue. EMPs will report on 2 types of bounces:

  • Soft bounces: Temporary delivery failures and can occur for a variety of reasons such as the subscriber’s server being down or inbox being full.
  • Hard bounces: Permanent delivery failures due to an invalid, erroneous address, an outdated domain, or an address which has fallen out of use.

A high bounce rate can indicate to email providers that your list is spammy. In turn, they’ll send your messages to bulk folders, thereby hurting deliverability. As a benchmark, aim to keep your list-wide bounce rate at 0.5% or lower.

Low Open Rates

An open rate is the number of people that open your email divided by the number of people it was sent to. If your open rate is very low, it could be due to the quality of the emails on your list, or your list’s level of engagement. As a benchmark, aim to keep open rate over 2.5%, the nonprofit average as reported by Mailchimp.
If you have a low open rate and a high bounce rate, your list might have too many spammy, old, or erroneous emails. Emails to these addresses bounce and go unopened.
If you have a low open rate but your bounce rate is healthy, this could mean that your subscribers are simply no longer interested in your content, that you aren’t sending on days or times that work for them, or that your subject lines are not effective.


The Nonprofit Organization’s Guide to Email Marketing

From lead generation to email segmentation to A/B testing, this guide is a one-stop-shop for bringing your email marketing strategy to the next level.

Clean it Up: Double Opt-in, SPF, Winback Campaigns

Now that you know what the indicators of an unhygienic email list are, which factors are impacting your list? It may be that your bounce rate is particularly high. Or it could mean that over time your open rates have plummeted or that open rates have always been low. It could also be a combination. We have solutions for all. Below are 3 ways to clean up your list and keep it clean over time in order of priority.

Double Opt-In

A double opt-in asks subscribers to confirm they want to be added to your list before your email marketing provider actually collects their data. With a double opt-in, your email service provider will ask users to confirm their subscription. This sets your list up for a clean future without any misspelled or erroneous emails. Plus, if someone doesn’t check their email enough to notice a confirmation after signing up, that’s a solid indicator that they won’t be as engaged with your emails over time.


No, not sunscreen. In the email marketing world, SPF stands for Sender Policy Framework, which is an email authentication method designed to detect fake sender addresses in emails, often used by people phishing and sending email spam. Most email marketing providers require multiple rounds of domain authentication to ensure you own your email address. SPF allows subscribers to check with your domain’s administrators. If your address isn’t authenticated, you could have deliverability issues down the line. Setting up an SPF in your email account will prevent any of those inquiries from diminishing your deliverability rates.

Winback Campaigns

If you have low open rates, this is the solution for you. Email marketing databases naturally degrade by about 22.5% every year, but acquiring a new customer is anywhere from five to 25 times more expensive than retaining an existing one. A winback campaign reminds subscribers why they signed up for your emails. It’s also an effort to re-engage and re-energize them for your cause. This type of campaign consists of 3-5 automated emails sent to anyone on your list that hasn’t opened your emails in 6 months or longer. By leveraging FOMO, incentives, and opt-in or out messaging, you can win over fatigued subscribers. Or you can open the door for them to unsubscribe with no hard feelings. In the end, you’ve either reminded subscribers of your organization, or you’ve prompted disengaged audiences to unsubscribe.

Bonus: A/B testing and manual check-ins

Double opt-ins, SPFs, and winback series are the best and most sustainable options for cleaning your list and keeping it clean. But it’s like dusting — there’s always more to be done.
If after cleaning your account your open rates are still below your benchmarks, we recommend A/B testing subject lines and send day or time. It may be that your messaging isn’t resonating, or your subscribers aren’t looking at their inboxes when you send.
If after cleaning your account and setting up a double opt-in you still have a high bounce rate, we recommend manually removing hard bounces from your list. Your email marketing provider should be doing this for you, but it might not be working as regularly as you need it to. If your tool isn’t cleaning our bounces, or isn’t doing so properly, it could mean there is a technical issue that you will need to reach out to their support team to resolve.

“What are email users doing on my site?” asked every nonprofit ever. With Lighthouse by Whole Whale, we’ve created a virtual handshake between your email marketing provider and your Google Analytics to better understand the online activities of high-value email subscribers. Get more information and sign up for a demo at