Monetize your Klaviyo email lists with newsletter ads
MailAdx works with Klaviyo's HTML blocks, and Klaviyo's sha_256 filter computes the subscriber hash at send time: {{ email|lower|sha_256 }}. Add open-time ad revenue to your Klaviyo campaigns and flows.
Why add MailAdx to Klaviyo?
How to integrate MailAdx with Klaviyo
- 1
Set up your MailAdx publisher account
Create a free account at mailadx.com/signup. After approval, access the Publisher Portal to create your ad placements.
- 2
Create an ad unit and copy the tag
In Publisher Portal → Ad Units, create a placement with your preferred format and floor CPM. Copy the HTML ad tag.
- 3
Use Klaviyo's sha_256 filter for the email hash
Klaviyo documents a sha_256 template filter, so the eh= value can be {{ email|lower|sha_256 }} with nothing stored on the profile. Klaviyo doesn't document the filter's output encoding, so confirm in a test send that it renders 64 lowercase hex characters. If it doesn't, store the hash as a profile property (email_sha256) and use {{ person.email_sha256|default:'' }}. Don't use person.id or the md5_hash filter: MailAdx accepts SHA-256 only.
- 4
Insert the ad tag via HTML block
In your Klaviyo template editor, add an HTML block. Paste the MailAdx ad tag and replace every {{EMAIL_SHA256}} placeholder with {{ email|lower|sha_256 }}.
- 5
Test with a preview send
Send a preview to yourself. Open the email and confirm the ad loads. Check the Publisher Portal for the test impression.
Klaviyo editor tips
Klaviyo's drag-and-drop editor has an HTML block under 'Basic' elements. For flow emails, edit the flow message template directly. If you use Klaviyo's universal content blocks, add the ad tag to the shared block so every campaign inherits it.
<!-- MailAdx ad tag — decision runs at open time -->
<a href="https://mailadx.com/api/v1/serving/click?pub=YOUR_PUB&pk=header&eh={{EMAIL_SHA256}}"
target="_blank">
<img src="https://mailadx.com/api/v1/serving/display?pub=YOUR_PUB&pk=header&eh={{EMAIL_SHA256}}&w=600&h=100"
width="600" height="100" alt="" />
</a>
<!-- Replace {{EMAIL_SHA256}} with your ESP's email hash merge tag -->Klaviyo + MailAdx: common questions
Does Klaviyo support SHA-256 email hashing natively?
Yes. Klaviyo's template language has a documented sha_256 filter, so {{ email|lower|sha_256 }} computes the hash at send time. Check one test send for 64 lowercase hex characters before you rely on it. A stored email_sha256 profile property is the fallback.
Should I use Klaviyo flows or campaigns for ad sends?
Both work. Add the ad tag to shared flow templates for recurring automations, or to one-off campaign templates for newsletters. The open-time auction runs the same way regardless of trigger type.
Billing with Klaviyo
MailAdx bills publishers a flat platform fee per impression served — typically $0.30–$0.50 per 1,000 impressions — regardless of which ESP you use. Your Klaviyo subscription fee is separate; MailAdx does not charge per send or per subscriber. Advertisers pay you directly (or via programmatic demand) above the platform fee. Top up credits in the Publisher Portal before going live; impressions pause gracefully when credits reach zero.
Troubleshooting Klaviyo + MailAdx
Ad image shows as broken or blank
Confirm the email-hash merge field substitutes in a real Klaviyo test send — not just the editor preview. An empty hash causes MailAdx to skip the auction. Re-send a test to yourself, view the raw HTML source, and verify the eh= parameter is populated.
Impressions not appearing in Publisher Portal
Open the test email in a client that loads remote images (Gmail web, Apple Mail with images enabled). Some corporate Outlook configs block external images by default. Wait 60 seconds and refresh the portal — reporting is near-real-time.
Merge field syntax error in template
Each ESP uses different personalization syntax. Double-check you replaced {{EMAIL_SHA256}} in the MailAdx tag with Klaviyo's exact variable from the setup steps above. A typo in the merge tag will break the URL at open time.
Related resources
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