Why list hygiene makes or breaks deliverability
Keeping your lists clean inside Klaviyo is one of the most effective ways to protect your sender reputation. When you carry invalid or dormant addresses, inbox providers like Gmail and Yahoo take notice. Your open rates drop, your bounce rates spike, and your emails start landing in the spam folder instead of the primary inbox.
We routinely aim for open rates above 50% and click rates above 2% across our clients' accounts. Achieving those numbers is nearly impossible if 10% to 15% of your list is dead weight. Regular cleaning also lowers your monthly Klaviyo invoice because you stop paying to store unusable profiles.
Bad data kills good deliverability.
When you should clean your contacts
You do not need to scrub your entire database every single week, but there are specific scenarios where list verification is mandatory before sending another campaign.
- Acquiring an existing business: You inherit an old customer database with unknown data collection standards.
- Re-engaging a lapsed audience: You have not emailed a segment of your list for six months or longer.
- Running public giveaways: Competitions attract fake addresses, throwaway accounts, and spam bots looking for freebies.
- Platform migrations: Moving from an older ESP like Mailchimp over to Klaviyo.
If any of these apply to your store, running a verification check will save you significant headaches down the road.
Exporting your list and running BounceBan
There are several list-cleaning tools on the market, but I prefer using BounceBan. It is straightforward, reliable, and reasonably priced. You can buy pay-as-you-go credits for roughly $40 per 10,000 emails, which easily covers most routine cleanups.
Start by locating the segment or list inside Klaviyo that needs verification. Navigate to Lists & Segments, select your target list, click Manage List, and choose Export List to CSV. I like to export only the email column to keep the file lightweight and quick to process.
Head over to BounceBan, go to the Bulk tab, and click New Task. Drag and drop your exported CSV into the upload box. Select the column header containing your emails, enable automatic file generation, and start the verification task. In a typical batch, you might find that 82% of the addresses are deliverable while around 12.5% are completely undeliverable.
Here is the critical distinction: if you are cleaning an existing Klaviyo list to clean up your current database, set your export settings in BounceBan to export all undeliverable emails.
Formatting and importing undeliverable addresses
Once BounceBan finishes processing, download the CSV containing your undeliverable contacts. Occasionally, the exported CSV contains extra metadata columns or duplicate headers that Klaviyo will reject during upload.
Open the file in Google Sheets or Excel. Delete any additional columns to the left or right so that only the raw email addresses remain. Label the top header cell exactly as Email, then download the cleaned sheet as a new CSV file.
Back inside Klaviyo, create a brand-new list and name it something obvious, such as Suppressed Bad Emails. Click Upload Contacts and upload your prepared CSV. When Klaviyo asks for the subscription status, select Import without updating subscription status. That is critical because you do not want to accidentally mark invalid addresses as subscribed profiles.
Suppressing invalid profiles across your account
Uploading those invalid addresses to a temporary list will not increase your Klaviyo bill. Klaviyo does not charge you double for re-uploading existing profiles, provided you handle their suppression status correctly.
Once the import completes, stay inside that newly created list. Click Manage List in the top right corner, then select Suppress current members and confirm the bulk suppression. Klaviyo will immediately apply a global suppression rule to every contact in that list.
Once suppressed, these contacts will never receive another campaign or flow email from your store, safeguarding your sender reputation instantly.
How to clean a list during a platform migration
The process differs slightly if you are migrating contacts from a third-party platform into a brand-new Klaviyo account. In that scenario, you do not want bad contacts entering Klaviyo in the first place.
Export your full subscriber database from your previous provider and run it through BounceBan. This time, configure BounceBan to export all deliverable emails only. You discard the undeliverable file entirely.
Take the verified deliverable CSV and upload it directly into your primary newsletter list in Klaviyo. During the import dialogue, set their subscription status to Subscribed (assuming these users explicitly opted in originally). This ensures your new Klaviyo account starts with pristine sender reputation from day one.
Final Thoughts
List cleaning is not glamorous work, but it directly protects your inbox placement and keeps your marketing overheads lean. Running a verification check before launching campaigns to unverified contacts will save your domain reputation from serious harm. Clean your data first, send second.
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