The savemms action

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The savemms action creates an MMS template, transcodes the content, and stores it for later use. A saved MMS template can be sent later by using sendsavedmms with the returned mms-id.

The MMS may contain slides with text and supported media objects such as image, audio, video, contact, calendar, PDF, and Excel content where enabled for the account.

When the template is successfully saved and transcoded, an N003 postback is generated. If audio or video content requires encoding, the template may not be immediately available for sendsavedmms. Attempting to send the template before encoding completes may return E626.

Endpoint and headers

POST https://api.ci.mblox.com/ep/v2/
Content-Type: application/json; charset=utf-8
x-api-key: YOUR_API_KEY_HERE

Request parameters

Slide parameters

Fallback SMS considerations

If an MMS is too large to deliver or if a carrier does not support MMS delivery, the API may deliver the content as fallback SMS if enabled. Fallback SMS consists of fallback-sms-text and, by default, a link to view the MMS content.

Content transcoding

When transcoding is enabled for the account, Sinch may reformat supported content so it can be delivered to the destination handset. Delivery success takes priority over image, audio, or video quality. Content may be reduced in quality to satisfy carrier and handset size restrictions.

The following content is never transcoded: contact, calendar, pdf.

Special considerations

• Media URLs must include the full absolute path, including http:// or https://.
• The hosting server must return a valid Content-Length header.
• The hosting server must return a valid Content-Type header.
• Chunked transfer encoding may be rejected if a Content-Length header is not provided.
• Accepted HTTP status codes for media retrieval are 200, 301, 302, 303, 307, and 308.
• For 3xx redirects, only one redirect is followed.
• Each MMS must include at least one slide.
• A maximum of 8 slides per submission is supported in this implementation.
• Each slide may include message-text and one supported media/object type.
• Do not include more than one file of the same MIME type on the same slide.
• Object slides such as contact, calendar, PDF, and Excel should not be combined with image, audio, or video.
• Unicode characters may not be supported in the subject of an MMS message.
• Slides with text support Unicode characters, including emoji or emoticon. Destination devices may have limited Unicode capabilities. The preferred encoding is UTF-8.

Example: Save MMS template

curl -i -X POST \
  https://api.ci.mblox.com/ep/v2/ \
  -H 'Content-Type: application/json; charset=utf-8' \
  -H 'x-api-key: YOUR_API_KEY_HERE' \
  -d '{
    "action": "savemms",
    "message-subject": "Monthly Update",
    "fallback-sms-text": "We could not deliver the MMS. View it here:",
    "disable-fallback-sms": false,
    "disable-fallback-sms-link": false,
    "client-reference": "template-build-001",
    "name": "monthly-update-template",
    "slide": [
      {
        "image": {
          "url": "https://example.com/content/update.png"
        },
        "message-text": "Here is this month's update."
      },
      {
        "pdf": {
          "url": "https://example.com/content/details.pdf"
        },
        "message-text": "See the attached PDF for details."
      }
    ]
  }'

Success response example

{
  "status": "success",
  "mms-id": "123456",
  "status-details": "MMS saved successfully."
}

Failure response example

{
  "status": "failure",
  "error-code": "E311",
  "error-info": "Invalid MMS Name or MMS Name is required."
}

Postback notification: Saved MMS ready

When a saved MMS has completed transcoding and is available to send, an N003 postback is generated.

{
  "origin": "MMS_MT",
  "code": "N003",
  "status": "Transcoding successful",
  "status-details": "MMS template is available for sending.",
  "mms-id": "123456",
  "tracking-id": "template-build-001",
  "client-reference": "template-build-001",
  "timestamp": "2026-04-24T18:33:00Z"
}

Response schema