Earning beyond Substack's platform with MailAdx
Substack limits direct HTML injection in emails, but MailAdx can still monetize your Substack audience via RSS-to-email tools, cross-posting setups, or when you export your list to a secondary ESP.
Why add MailAdx to Substack?
How to integrate MailAdx with Substack
- 1
Export your Substack subscriber list
In Substack Settings → Subscribers, export your subscriber list as a CSV. This gives you your subscribers' email addresses to use with a separate ESP.
- 2
Set up a secondary ESP for ad sends
Import your Substack subscribers into a secondary ESP (Beehiiv, Mailchimp, or Klaviyo) that supports MailAdx's ad tag integration. Some publishers cross-post to a secondary ESP for their ad-supported send while keeping Substack for paid subscribers.
- 3
Connect MailAdx to your secondary ESP
Follow the MailAdx integration guide for your chosen ESP. Paste the ad tag into your template with the email hash merge field.
- 4
Set up your monetization strategy
Many publishers run two sends: a Substack-native send for paid subscribers and an ad-supported send for free subscribers via MailAdx + secondary ESP.
Substack editor tips
Substack does not allow third-party HTML in native sends. This guide covers the export-and-secondary-ESP workflow. If you use a Beehiiv or Mailchimp mirror list, follow that ESP's integration guide for the ad tag placement.
<!-- 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 -->Substack + MailAdx: common questions
Can I add MailAdx ads directly to Substack emails?
Substack does not allow custom HTML or third-party ad tags in email sends. The recommended approach is to export your subscriber list and use a secondary ESP for ad-supported sends, while keeping Substack for your paid content.
Is this compliant with Substack's terms?
Exporting your subscriber list and using it on another platform is permitted under Substack's terms — you own your subscriber relationships. The MailAdx integration would run entirely outside of Substack's platform.
Can I monetize Substack free subscribers with MailAdx?
Yes — export free-tier subscribers and import them into a secondary ESP (Beehiiv, Mailchimp) for ad-supported sends. Keep paid subscribers on Substack-native sends without ads if you prefer.
Will Substack know I'm using MailAdx?
No. Ad-supported sends run entirely through your secondary ESP. Substack only handles the sends you still route through their platform.
Billing with Substack
MailAdx bills publishers a flat platform fee per impression served — typically $0.30–$0.50 CPM — regardless of which ESP you use. Your Substack 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 Substack + MailAdx
Subscriber export is incomplete
Substack exports include only active subscribers. Re-export after major list growth events. Deduplicate against your secondary ESP before importing to avoid double sends.
Paid vs free list segmentation
Tag paid Substack subscribers separately in your secondary ESP so you do not send ad-supported emails to people who pay for ad-free content.
Import CSV hash column missing
Pre-compute SHA-256 hashes in your CSV before import, or use your ESP's API to hash on contact create. MailAdx support can provide a one-line script for bulk hashing.
Related resources
Ready to monetize your Substack newsletter?
Free to start. No revenue share. Direct advertiser relationships from day one.