Scheduling emails for future delivery requires just one additional field — scheduledAt — added to both the standard Transactional or Marketing Email request body. No client-side timers or queues needed.

How it works

Pass a scheduledAt value in ISO 8601 format (e.g. 2026-06-10T15:30:00+02:00) in your send request

Emails can be scheduled up to 72 hours in advance

The API responds immediately with 202 Accepted confirming the request was received

The email is then held in the sending infrastructure and delivered automatically at the scheduled time

Request Parameters

Scheduling uses the same request body as the standard Transactional Email and Marketing Email APIs with one additional field: scheduledAt.

Query Parameters

Body Parameters

scheduledAt Field

Edge cases:

• If scheduledAt is in the past, the API returns 400 — the email is not sent.
• If scheduledAt exceeds the 72-hour window, the API returns 400 — the email is not queued.
• In both cases the response body includes a descriptive message field. See Response Codes below.

Example

Transactional

POST https://api.cm.com/email/gateway/v1/transactional?priority=high
Content-Type: application/json
X-CM-PRODUCTTOKEN: {your-product-token}

{
  "from": { "email": "[email protected]", "name": "Sender Name" },
  "to": [{ "email": "[email protected]", "name": "Recipient Name" }],
  "scheduledAt": "2026-06-10T18:14:00+02:00",
  "subject": "Email Subject",
  "html": "<p>HTML content</p>",
  "text": "Plain text content",
  "customerReference": "your-reference"
}

Marketing

POST https://api.cm.com/email/gateway/v1/marketing
Content-Type: application/json
X-CM-PRODUCTTOKEN: {your-product-token}

{
  "from": { "email": "[email protected]", "name": "Sender Name" },
  "to": [{ "email": "[email protected]", "name": "Recipient Name" }],
  "scheduledAt": "2026-06-10T18:14:00+02:00",
  "subject": "Email Subject",
  "html": "<p>HTML content</p>",
  "text": "Plain text content"
}

Response

{
  "status": 202,
  "message": "Accepted",
  "success": true,
  "messageId": "7526bb32-c174-4bad-9c35-dba08f8667aa",
  "batchId": "cd288015-0080-450f-98dd-60eafcfa3df6"
}

Response Codes

Common 400 errors

scheduledAt in the past:

{
  "status": 400,
  "message": "ScheduledAt must be in the future.",
  "success": false,
  "messageId": ""
}

scheduledAt exceeds 72-hour limit:

{
  "status": 400,
  "message": "ScheduledAt cannot be more than 72 hours in the future.",
  "success": false,
  "messageId": ""
}

Webhook events

New webhook event type is available for scheduled emails:

• Scheduled — fired once the email is confirmed as queued for delivery at the scheduled time

Scheduled event payload:

{
  "type": "scheduled",
  "createdAt": "2026-06-12T10:44:17+00:00",
  "messageId": "d2d6f36f-122f-4d70-bfef-2b1522c87cec",
  "data": {
    "to": "[email protected]",
    "from": "[email protected]",
    "id": "bff72c14-4c5b-4c81-938f-a344ed278372",
    "customerReference": "",
    "scheduled": {
      "scheduledAt": "2026-06-12T10:45:00+00:00",
      "message": "Email is scheduled to be sent at June 12, 2026 at 10:45 UTC."
    }
  }
}

📌

Note: Cancellation of scheduled emails is not yet supported via the API. The cancelled webhook event will become available in an upcoming release.

Message Logs

In the Email Logs page, scheduled emails will appear with a Scheduled status. Once the email is delivered at the scheduled time, the status will automatically update to Delivered.