Auto-Publish ACS Content to Substack via Zapier

This guide walks through the complete setup to automatically deliver ACS-generated newsletters to your Substack publication using Zapier as the bridge.

Overview

Substack does not offer a programmatic publishing API, but it does provide a unique import email address for each publication. Emails sent to this address are automatically created as draft posts. This tutorial uses Zapier's Email action to forward ACS content to Substack.

The flow: ACS publishes → Outbound webhook → Zapier Catch Hook → Email sent to Substack import address → Draft created in Substack

What You Will Need

• ACS with the Newsletter channel configured and a publishing platform connected
• A Zapier account (free tier works)
• Your Substack publication's import email address

Step 1: Find Your Substack Import Email

1. Log into Substack and go to your publication's Dashboard
2. Navigate to Settings → Import
3. Your import email address is listed there
4. Copy it — this is where Zapier will deliver the newsletter

Step 2: Create the Outbound Webhook in ACS

1. Go to Settings → Integrations → Outbound Webhooks → Add Destination
2. Label it "Substack"
3. Leave the Destination URL blank for now
4. Save

Step 3: Set Up the Zapier Trigger

1. In Zapier, click Create Zap
2. Select Webhooks by Zapier → Catch Hook as the trigger
3. Copy the webhook URL Zapier generates
4. Click Continue

Step 4: Link ACS to the Zap

1. In ACS, edit your Substack destination
2. Paste the Zapier URL as the Destination URL
3. Save
4. Click Send Test to fire a test payload to Zapier

Step 5: Load the Payload in Zapier

Back in Zapier, click Test trigger. Zapier should receive the ACS test payload and display the available fields. Confirm you can see:

• subject_line — the newsletter subject
• body_html — the HTML newsletter body
• preheader_text — the email preheader

Step 6: Add the Email Action

1. Click + to add an action
2. Search for and select Email by Zapier → Send Outbound Email
3. Configure the email fields:
   • To: Your Substack import email address (type it directly, do not map from ACS data)
   • Subject: Map to subject_line from the ACS payload
   • Body: Map to body_html
   • Body Type: Select HTML
4. Click Test action

Check your Substack drafts — the newsletter should appear as a new draft post within a minute or two.

Step 7: Activate the Zap

Once the test succeeds, click Publish Zap. Every future ACS newsletter will automatically appear in your Substack drafts.

About Draft-Only Publishing

Substack's import process creates drafts — it does not send to subscribers automatically. You will still need to review and send from your Substack dashboard. This is intentional: it gives you a final review checkpoint before the newsletter reaches your audience.

Troubleshooting

Draft not appearing in Substack Send a manual test email to your Substack import address from your regular email client to confirm the address is correct and active.

Subject line is empty in Substack Ensure you mapped subject_line to the email subject field, not title. For newsletters, subject_line contains the properly formatted email subject.

Broken formatting in Substack Try the body (plain text) field instead of body_html. Substack's import processor may not fully support all HTML structures.