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Sometimes the content you need in an email lives outside Maestra Platform—a showtime catalog, live inventory, or personalized offers from your own service. And it’s not a single field: it’s arrays of data you need to loop through and render into the email layout. Webhook-powered content lets you do that directly from the campaign template, no custom integration required. This guide walks you through the setup.

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Step 1. Create an integration

Go to Integrations → Add integration, pick the Webhook Integration preset, and fill in:
  • URL — the base URL of your service. You can specify just the root and add path-specific parts in each webhook separately.
  • Headers — Authorization, Content-Type, and anything else your API requires.
  • Request rate limit per second — set to Not specified so Maestra doesn’t rate-limit outbound sends.

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Step 2. Create a webhook with “Use full response as campaign content”

Inside the integration, click Create to add a webhook. Fill in the name, system name, method, and path. In the Response settings block, select “Use full response as campaign content”.
Webhooks support two modes:
  • Map specific fields — the existing behavior. Used for integrations and response checks inside flow scenarios: individual values are pulled from the response by path and saved in a flow session for use in Condition nodes or campaigns as individual data points.
  • Use full response as campaign content — the new mode. The entire JSON response becomes available inside the campaign template, where you can iterate it with for…end for, branch with if, and render content directly in your email block using Dynamic parameters.
Save the webhook.
Do not use dashes in the webhook system name. Use camelCase or snake_case instead.

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Step 3. Reference the webhook in your campaign

Open a campaign and reference the webhook response using this parameter syntax: 
ExternalData.YourWebhookSystemName
After the webhook name, use dot notation to navigate to specific JSON nodes.

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Example: Angel Studios

The Angel API returns a nested response like this: 
{
  "venues": [
    {
      "name": "Classic Cinemas Fox Lake Theatre",
      "address_text": "115 Towne Centre Lane, Fox Lake, IL",
      "showtimes_by_day": [
        {
          "date": "2026-07-03",
          "showtimes": [
            {
              "local_start_time_friendly": "11:15 AM",
              "ticket_url": "https://www.angel.com/tickets/..."
            }
          ]
        }
      ]
    }
  ]
}
In the campaign’s HTML block, use nested loops to render the full structure: 
@{ for venue in ExternalData.AngelWebhookYoungWashingtonLaunchDate.venues }
  <h3>${ venue.name }</h3>
  <div>${ venue.address_text }</div>

  @{ for day in venue.showtimes_by_day }
    <strong>${ day.date }</strong>
    @{ for showtime in day.showtimes }
      <a href="${ showtime.ticket_url }">
        ${ showtime.local_start_time_friendly }
      </a>
    @{ end for }
  @{ end for }
@{ end for }
Three levels of nesting—venues → showtimes_by_day → showtimes—are iterated with three nested for…end for loops. Fields within each object are accessed with dot notation: venue.name, day.date, showtime.ticket_url.

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Step 4. Send the campaign

At send time, Maestra Platform calls your endpoint for each recipient, waits for the response, and injects the data into the email before delivery.

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What happens if the webhook doesn’t respond

If the call to your endpoint fails, the email is not sent to that recipient. The rest of the campaign continues normally—only the affected recipients are skipped. Before skipping, the system retries automatically:
  1. 3 attempts on 429 and 5xx errors
  2. 1-minute pause
  3. Up to 2 more retry cycles
A recipient is only skipped if all retry attempts fail.

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Debugging

Every webhook call is logged. Go to Integrations → Webhooks → Webhook logs to see the full request URL, headers, response body, and HTTP status. If something looks off, that’s your starting point.