Add programmatic and direct ad revenue to your Mailchimp newsletter
MailAdx integrates with Mailchimp through a standard HTML content block and an *|EMAIL_SHA256|* audience field that holds each contact's SHA-256 email hash. Monetize your Mailchimp audience with open-time ads.
Why add MailAdx to Mailchimp?
How to integrate MailAdx with Mailchimp
- 1
Create your MailAdx publisher account
Sign up at mailadx.com/signup and get approved (up to 24 hours). No credit card required.
- 2
Create an ad placement and copy the ad tag
In the Publisher Portal, create a new Ad Unit. Set your floor CPM and format. Copy the generated HTML ad tag.
- 3
Create and fill an EMAIL_SHA256 audience field
Mailchimp has no merge tag that hashes an email address. Create a text audience field with merge tag EMAIL_SHA256, and fill it with sha256(lower-cased email) as lowercase hex: import a CSV for existing contacts, and use the Mailchimp API (for example from a Subscribes webhook) for new ones. Contacts with an empty field get no ad. If you can't maintain the field, *|URL:EMAIL|* in eh= sends the raw address for MailAdx to hash on receipt, but then the plaintext address is in the ad URL.
- 4
Add an HTML content block to your Mailchimp template
In the Mailchimp email editor, drag a Code block (or Custom HTML block) into your template where you want the ad. Paste the MailAdx ad tag, replacing {{EMAIL_SHA256}} with *|EMAIL_SHA256|*.
- 5
Preview and test
Send a test to a contact whose EMAIL_SHA256 field is filled in. In the received email, eh= should be 64 lowercase hex characters. Open the email, confirm the ad loads, and check the impression in your Publisher Portal.
Mailchimp editor tips
Use Mailchimp's Code block (drag from Content → Code) in the new email builder. Legacy templates use the Custom HTML merge tag area. Always send a live test to a real list member — Mailchimp's generic preview may not substitute merge tags correctly.
<!-- 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 -->Mailchimp + MailAdx: common questions
Does MailAdx replace Mailchimp Ads?
MailAdx is a replacement for Mailchimp's passive ad network for publishers who want more control. You own the advertiser relationship, set your own floors, and access programmatic demand beyond Mailchimp's marketplace.
Which Mailchimp plans support HTML blocks?
Custom HTML blocks are available on Mailchimp's Essentials, Standard, and Premium plans. The free plan has limited template customization — check your plan's template editor for the Code block option.
How does billing work when I send through Mailchimp?
You pay Mailchimp for email delivery as usual. MailAdx charges only when a subscriber opens and the ad image is requested — not when Mailchimp sends the email. A 10,000-recipient send with a 35% open rate generates roughly 3,500 billable impressions, not 10,000.
Can I use multiple ad placements in one Mailchimp template?
Yes. Create separate ad units in MailAdx (e.g., header, mid-roll, footer) and paste each tag in a different HTML block. Each placement has its own floor CPM and reporting in the Publisher Portal.
Does the Mailchimp integration work on mobile email clients?
Yes. MailAdx serves standard HTML image tags that render in Gmail iOS/Android, Apple Mail, Yahoo, and Outlook mobile. No JavaScript runs inside the inbox — the ad is a plain image request at open time.
Billing with Mailchimp
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 Mailchimp 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 Mailchimp + MailAdx
Ad image shows as broken or blank
Confirm the email-hash merge field substitutes in a real Mailchimp 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 Mailchimp's exact variable from the setup steps above. A typo in the merge tag will break the URL at open time.
Ready to monetize your Mailchimp newsletter?
Free to start. No revenue share on direct-sold. Advertiser relationships you own from day one.