How to clean an email list

Clean a Klaviyo email list in stages: let bounces suppress, exclude unengaged profiles from campaigns, give them a sunset flow, then suppress who stays silent.

What this is for

Every email you send to someone who never opens it tells Gmail, Yahoo and the rest that your mail is not wanted. Enough of those and your email starts landing in spam for the people who do want it. Gmail's own sender guidelines put the fix plainly. source, checked 28 September 2026

There is a cost side too. On Klaviyo, profiles you can still email count towards your plan, so people who will never buy again are costing you money every month. Cleaning in the order below removes them without cutting off a customer who is simply quiet for a while. source, checked 28 September 2026

Time needed and what you need

Time needed: about 2 hours, then 15 minutes a month. Building the segments and the sunset flow takes most of the first session; after that, cleaning is a monthly suppression and a check of the numbers.

Klaviyo access with permission to create segments, flows and suppressions
Your usual sending frequency, which sets how strict the unengaged segment should be
An export of your full profile list, kept somewhere safe before you suppress anyone
A short plain-text email you are happy to send as a last check-in

The steps

Steps 2 to 4 protect deliverability straight away. Steps 5 to 8 take a few weeks, because the sunset flow needs time to run.

1. Check that bounces are already being suppressed

You do not need to clean bounces by hand in Klaviyo. A hard bounce is suppressed at once. A soft bounce, such as a full inbox, is only suppressed after a run of them, so an address that fails now and then stays on your list. source, checked 28 September 2026

Open the suppressed profiles view and glance at the bounce reasons in the deliverability report. If one mailbox provider is bouncing far more than the others, that is a sender reputation issue to fix, not a list to prune.

2. Build an unengaged segment sized to how often you send

Create a segment of people who can receive email, have been sent several of your emails, and have not opened or clicked in the last 90 days. If you email daily or several times a week, tighten that to 30 days. If you moved from another platform recently, include the opens and clicks you imported, or new arrivals will look unengaged when they are not. source, checked 28 September 2026

3. Exclude that segment from campaigns

In every campaign's recipient settings, put the unengaged segment in the exclusion box. This is the single change that does the most for deliverability, and it is reversible: if someone clicks a flow email or buys, they leave the segment and start receiving campaigns again. source, checked 28 September 2026

Make an exception for your two or three biggest sends of the year, such as a launch or Black Friday, if you choose. Everything else goes to engaged people only.

4. Decide which flows unengaged people can still enter

Keep abandoned checkout and similar flows open to everyone: someone who starts a checkout is engaged, whatever their email history says. Exclude unengaged profiles from flows that fire often, such as browse abandonment, where one person can trigger several emails in a week. Past customers who have gone quiet are a separate job: they get a winback sequence before anyone thinks about suppressing them. source, checked 28 September 2026

5. Build the sunset segment for long-term silence

The unengaged segment is people who have gone quiet. The sunset segment is people who were never there: they have received at least five emails over the last 72 weeks and have never opened, clicked, visited the site, viewed a product, started a checkout or placed an order. Klaviyo offers this as a ready-made Sunset (Email) segment in its segment library. source, checked 28 September 2026

6. Send them a short sunset flow

Create a flow triggered by joining the sunset segment, starting from Klaviyo's pre-built sunset flow if you like. Add a flow filter so anyone who opens or clicks leaves the flow. Then write one to three short emails that ask, plainly, whether they still want to hear from you, with a clear way to change preferences or unsubscribe. source, checked 28 September 2026

Plain text, from a person at the shop
Subject that says what is happening, such as "Should we stop emailing you?"
One link to browse new products, one to update preferences

7. Give a grace period, then tag who stayed silent

After the last email, add a short delay so people have time to open it, then an update profile property action that sets a property such as Unengaged to true. Klaviyo's example gives three days if you send daily and longer if you send less often. source, checked 28 September 2026

8. Suppress the tagged profiles before each campaign

Make a segment of everyone with Unengaged set to true, then use Suppress current members on it. Suppression only covers the people in the segment at that moment and Klaviyo cannot suppress from inside a flow, so repeat it before each campaign or on a fixed day each month. source, checked 28 September 2026

A worked example

For a pet supply store with 30,000 email subscribers
Worked example (an invented store, with invented numbers)
The store sends two campaigns a week, so it uses a 90-day unengaged segment. It holds 9,000 profiles, which leaves 21,000 people on each regular campaign.
4,200 of those 9,000 also match the sunset segment and enter the sunset flow. 380 open or click and leave the flow, and 150 unsubscribe. The remaining 3,670 are tagged Unengaged and suppressed (4,200 - 380 - 150 = 3,670).
Those 3,670 no longer count as emailable profiles on the store's plan, and the 380 who re-engaged drop out of the unengaged segment and start getting campaigns again.

Common mistakes

Deleting unengaged profiles instead of suppressing them. Deleted profiles can come back through an import or a sign-up with no record of why they left. Suppression keeps the history and still stops the sends.

Mailing an old, untouched list all at once to see who is still there. Klaviyo warns that addresses with no engagement for over a year put deliverability at risk, and a large blast to them can do more damage than the cleaning repairs. Send in small batches, the way you would when warming a new sending domain. source, checked 28 September 2026

Suppressing once and calling the list clean. New people go quiet every week. If the suppression step is not on a calendar, the list drifts back to where it was within months.

Buying a list or importing contacts who never signed up, then trying to clean them. Gmail's guidelines say those recipients are likely to mark you as spam, and no sunset flow undoes that. source, checked 28 September 2026

Questions people ask

What is the difference between the unengaged segment and the sunset segment?

The unengaged segment is people who have not opened or clicked recently; you stop sending them campaigns but keep them. The sunset segment is people who have never engaged at all over a long stretch; they get a final check-in and are then suppressed. A person can drift into the first and back out again. The second is a goodbye.

Should I pay for an email verification service?

For your live list, usually not: Klaviyo already suppresses hard bounces and chronic soft bounces. For an old list you have not mailed in a long time, Klaviyo suggests running it through a cleaning service before any send. source, checked 28 September 2026

Will cleaning my list lower my revenue?

It lowers the number of emails sent, not the number of people who buy, because the people removed were not opening. Compare revenue per campaign before and after rather than list size. If deliverability was the problem, the engaged part of the list often sees more of your mail afterwards. To see what else affects opens, read writing subject lines that get opened.

See this on your own store

Paste your store URL. The first pass takes about a minute and needs no account. Save a card (nothing is charged) and Tilly reads the whole store and works out who buys from you.