Frequently Asked Questions
Use the Sinch MMS JSON API with Express.js and Node.js to create an API endpoint that accepts requests for sending multimedia messages. This involves setting up a Node.js project, installing required dependencies like Axios and Express, and implementing a service to interact with the Sinch API.
The Sinch MMS JSON API, specifically the XMS API endpoint, allows developers to send multimedia messages programmatically. It handles requests containing recipient details, message content, and media URLs for sending MMS messages via the Sinch platform.
Sinch requires a publicly accessible media URL so its servers can directly fetch the media content (images, audio, video) to include in the MMS message. Ensure your media hosting server includes the Content-Length header for Sinch to process correctly.
Use the Sinch MMS API when you need to send rich media content like images, audio, or video along with your messages. SMS is limited to plain text, making MMS essential for marketing campaigns, notifications with visuals, or other communication needing more than text.
The article doesn't explicitly address international MMS. However, it does mention E.164 number formatting for the "SINCH_MMS_NUMBER" environment variable, implying international number support might be available. Consult the official Sinch documentation for details on supported countries and regions for sending international MMS messages.
Initialize a Node.js project using npm init, then install necessary packages such as express, axios, dotenv, and winston. Configure environment variables like SINCH_SERVICE_PLAN_ID and SINCH_API_TOKEN in a .env file to securely store your Sinch credentials.
Axios, a promise-based HTTP client, is used to make POST requests to the Sinch XMS API. It simplifies sending the MMS payload to Sinch and handles the API responses.
The example code provides error handling at multiple levels. Input validation using express-validator catches bad requests, authentication middleware handles unauthorized access, and a try-catch block in the Sinch service manages errors during API calls. Winston logs error details for debugging.
Winston provides structured logging with different levels (debug, info, warn, error), facilitating efficient debugging and monitoring. It's configured to log timestamps, stack traces, and specific error data for better insight into API interactions and potential issues.
You need a Sinch account with an active MMS API subscription, a provisioned phone number (Short Code, Toll-Free, or 10DLC) enabled for MMS, Sinch Service Plan ID and API Token, and a publicly accessible URL for your media file. Node.js and npm must also be installed.
Secure your integration by storing Sinch credentials as environment variables, never committing your .env file, and using a strong, random API key for authentication (INTERNAL_API_KEY) to protect your Express API endpoint. Use HTTPS and consider rate limiting with express-rate-limit and security headers with Helmet.
The article recommends creating separate directories for routes, controllers, services, middleware, and configuration files. Place your main server logic in server.js. This structure promotes code organization and makes future updates or extensions easier.
The article doesn't specify Sinch's rate limits. Refer to the official Sinch documentation for details on rate limits, as exceeding them can lead to throttled or rejected requests. Consider implementing your own rate limiting using express-rate-limit.
The code uses axios-retry to automatically retry failed Axios requests to the Sinch API. It retries on network errors or 5xx server errors with exponential backoff (1s, 2s, 3s delays between retries), increasing resilience to temporary issues.
Send MMS with Sinch in Node.js Express: Complete Implementation Guide
Learn how to build a production-ready Node.js application using Express to send MMS (Multimedia Messaging Service) messages via the Sinch API. This comprehensive tutorial covers project setup, MMS implementation, API creation, error handling, security best practices, and deployment.
By the end, you'll have a functional Express API endpoint that sends MMS messages with images, videos, or audio files using the Sinch XMS API and your Sinch account credentials.
What Will You Build with Sinch MMS?
Goal: Create a reliable backend service that sends MMS messages programmatically using Sinch.
Problem Solved: Automate sending rich media messages (images, audio, video) to users – essential for notifications, marketing campaigns, appointment reminders with QR codes, customer support with visual instructions, e-commerce order confirmations with product images, and event invitations with venue photos.
When to Use MMS vs. SMS:
Common Use Cases:
Technologies:
.envfile/batchesendpoint withmt_mediatypeCompatibility Notes:
System Architecture:
Prerequisites:
Content-Typeheader (e.g.,image/jpeg,video/mp4) and aContent-Lengthheader.Media Hosting Solutions:
Choose a reliable hosting solution for your MMS media files:
Source: Sinch MMS Support Documentation
MMS File Size Limits and Best Practices:
Content-Typeheader (e.g.,text/plain,image/gif,audio/mp3,video/mp4)File Size Calculation Examples:
What Happens When Files Exceed Limits:
Source: Sinch MMS Best Practices
Supported Media Types:
Format-Specific Recommendations:
Source: Sinch MMS Sizes and Limitations
How Do You Set Up Your Node.js Project for Sinch MMS?
Initialize your Node.js project and install the necessary dependencies for sending MMS messages with Sinch.
Create Project Directory: Open your terminal and create a new directory for the project.
Initialize Node.js Project: Create a
package.jsonfile.Enable ES Modules: Use
import/exportsyntax by adding"type": "module"to yourpackage.json. Alternatively_ rename all.jsfiles to.mjs. Openpackage.jsonand add:Install Dependencies: Install Express_ Axios_ dotenv_ validation_ rate limiting_ security headers_ logging_ and retry libraries with pinned versions for production stability.
Install Development Dependencies: Install
nodemonfor automatic server restarts during development.Create Project Structure: Organize the code for better maintainability.
Configure
.gitignore: Prevent sensitive files and unnecessary modules from version control.Set Up Environment Variables (
.env): Store your sensitive credentials and configuration here. Never commit this file.PORT: Port the Express server listens onNODE_ENV: Environment type (development_production)SINCH_SERVICE_PLAN_ID_SINCH_API_TOKEN: Your credentials from the Sinch Dashboard (see Prerequisites)SINCH_MMS_NUMBER: The Sinch phone number you send MMS from (E.164 format)SINCH_API_BASE_URL: Base URL for the Sinch API region. Regional endpoints:us.sms.api.sinch.com(US) oreu.sms.api.sinch.com(EU). Choose based on your location and data protection requirements.INTERNAL_API_KEY: Crucial: Replace the placeholder with a cryptographically secure random string. This key protects your API endpoint.LOG_LEVEL: Controls logging verbosityEnvironment Variable Validation Strategy:
Add startup validation to catch configuration errors early. Create
src/config/validateEnv.js:Team Onboarding Template (.env.example):
Source: Sinch SMS API Reference
Add npm Scripts: Add scripts to
package.jsonfor running, linting, and testing the server.How Do You Implement the Sinch MMS Service in Node.js?
Create a dedicated service to handle interactions with the Sinch MMS API, incorporating logging and retry logic.
src/config/logger.jsLog Rotation and Retention:
For production environments, add log rotation to prevent disk space issues:
External Logging Integration:
For production monitoring, integrate with services like Datadog, New Relic, or Sentry:
src/services/sinchService.jsSinch API Error Codes:
400401402403404429500503Rate Limit Handling:
Implement custom rate limit detection and backoff:
Explanation:
winstonlogger./batchesendpoint using the format{region}.sms.api.sinch.com/xms/v1/{service_plan_id}/batches.axiosinstance with 30-second timeout and configuresaxios-retryto automatically retry requests on network errors or 5xx responses from Sinch, using exponential backoff. Logs retry attempts.sendMmsFunction:/batchesendpoint. Key fields includeto,from,body.type(must be"mt_media"),body.url,body.message, andbody.parameters(conditionally added).strict_validationparameter enables validation against Sinch MMS channel best practices.Content-TypeandContent-Lengthheaders.parametersormessagefields if not used.Content-TypeandAuthorization: Bearer.logger.info,logger.debug,logger.warn,logger.error). Logs payload at debug level.sinchAxiosinstance (with retry) to make thePOSTrequest.catchblock logs detailed error information and constructs a specific error message before re-throwing it.Performance Optimization:
axios.defaults.httpAgentSource: Sinch Batches API Reference
How Do You Build the Express API for Sending MMS?
Create the Express endpoint that uses the
sinchService.src/middleware/authMiddleware.jsAdvanced Authentication Options:
For production systems, consider implementing JWT or OAuth2:
Rate Limiting Per API Key:
Implement abuse prevention with per-key rate limiting:
src/controllers/mmsController.jsAsync Queue Implementation:
For high-volume scenarios, implement message queuing with Bull or BullMQ:
src/routes/mmsRoutes.jsMedia URL Validation Utility:
Add preemptive validation to catch hosting issues:
Test Media URLs with cURL:
Explanation:
authMiddleware.js): Checks forX-API-Keyheader against.env. Logs warnings if the key is missing or invalid.mmsController.js):validationResultto check for errors fromexpress-validator. Returns 400 if invalid.sendMmsservice function within atry…catchblock.202 Acceptedon success, including the service response.500 Internal Server Error.mmsRoutes.js):express-validator.POST /api/mms/sendroute.apiKeyAuth, validation rules, then the controller.GET /status/:batchIdendpoint to check delivery status.How Do You Integrate the Sinch MMS API?
Focus on the specific Sinch integration points.
Credentials:
SINCH_SERVICE_PLAN_ID,SINCH_API_TOKEN,SINCH_MMS_NUMBER,SINCH_API_BASE_URLin your.envfile (locally) and as secure environment variables in your deployment environment. Never commit.envor hardcode credentials.API Endpoint:
${SINCH_API_BASE_URL}/xms/v1/${SINCH_SERVICE_PLAN_ID}/batches.us.sms.api.sinch.com(United States) oreu.sms.api.sinch.com(European Union). Choose based on your location and data protection requirements.Source: Sinch SMS API Reference
Authentication:
Authorization: Bearer ${SINCH_API_TOKEN}header insinchService.js.Payload:
mt_mediatype within the/batchesstructure in your JSON payload. Set the type field tomt_mediafor MMS messages.messagefield of the body object.strict_validationfield to enable message validation against Sinch MMS channel best practices.Source: Sinch MMS Support Documentation
mediaUrlpublicly accessible via HTTP GET.Content-Lengthheader. Check usingcurl -I <your_media_url>.Content-Typeheader (e.g.,image/jpeg,video/mp4,audio/mp3).Source: Sinch MMS Best Practices
parameters.mms_fallback_textfield to control the SMS text if MMS fails.disable_fallback_sms_linkordisable_fallback_smsif needed.Fallback Failure Scenarios:
Understand when and how MMS falls back to SMS:
Testing Fallback:
Source: Sinch Batches API Documentation
How Do You Handle Errors and Implement Retries for MMS?
express-validatorin routesapiKeyAuthmiddlewaresinchService.jscatch block with retries viaaxios-retrycatchblock handles service errorswinstonfor structured, leveled logging (src/config/logger.js)console.*withlogger.*axios-retryinsinchService.jsMonitoring and Alerting:
Implement production monitoring with health checks and alerts:
Dead Letter Queue for Failed Messages:
Implement DLQ for messages that fail after all retries:
Frequently Asked Questions About Sending MMS with Sinch
What are the file size limits for Sinch MMS messages?
Keep media files under 1 MB – most MMS providers use this limit. Without transcoding, keep video and image files under 500 KB, with a maximum of 740 KB. With Sinch transcoding enabled, files under 1 MB work best. To estimate the final MMS size, multiply your file size by 1.37 and add 814 bytes for Base64 encoding headers that Sinch uses for MMS delivery.
Example: A 500 KB image becomes (500 KB × 1.37) + 814 bytes = approximately 685.8 KB after encoding.
Which media formats does Sinch support for MMS?
Sinch supports Images (GIF, JPG, PNG), Audio (MP3, WAV), Video (3GP, MP4, MPEG, MPG, AVI, WMV), and Text (TEXT/PLAIN). All media files must be served with a valid
Content-Typeheader (e.g.,image/jpeg,video/mp4,audio/mp3) and aContent-Lengthheader from publicly accessible URLs.How do you calculate Base64 encoding overhead for MMS?
Sinch delivers MMS messages in Base64 encoding. Calculate the final size by multiplying your file size by 1.37 and adding 814 bytes for headers. For example, a 500 KB image becomes approximately (500 KB × 1.37) + 814 bytes = 685.8 KB after encoding. This calculation helps ensure your media stays within the 1 MB MMS provider limit.
What is the mt_media type in Sinch API?
The
mt_mediatype is a required field in the Sinch XMS API/batchesendpoint for sending MMS messages. Setbody.typeto"mt_media"(mobile-terminated media message) to indicate you're sending MMS rather than plain SMS. This type enables thebody.urlfield where you specify the publicly accessible media URL.How do you enable MMS functionality in the US region?
In the US region, contact your Sinch account manager to enable MMS functionality for your Service Plan ID. Verify in the Sinch dashboard (under "Numbers" → "Your Numbers") that your chosen phone number has MMS sending capabilities enabled before attempting to send MMS messages. This requirement is specific to the US region.
What headers must media URLs return for Sinch MMS?
Media URLs must return two required headers:
Content-Type(e.g.,image/jpeg,video/mp4,audio/mp3) to specify the media format, andContent-Lengthto indicate file size. Test your media URL usingcurl -I <your_media_url>to verify both headers are present before sending MMS messages.What are the regional endpoint differences for Sinch?
Sinch offers two regional endpoints:
us.sms.api.sinch.com(United States) andeu.sms.api.sinch.com(European Union). Choose based on your location and data protection requirements. Configure theSINCH_API_BASE_URLenvironment variable with the appropriate regional endpoint. The full XMS API endpoint follows the format{region}.sms.api.sinch.com/xms/v1/{service_plan_id}/batches.How do you implement retry logic for failed MMS sends?
Use the
axios-retryplugin configured insinchService.jsto automatically retry failed requests. The implementation retries network errors or 5xx server responses from Sinch up to 3 times with exponential backoff (1s, 2s, 3s delays). The retry mechanism usesaxiosRetry.isNetworkOrIdempotentRequestError(error)to determine which errors warrant retries, ensuring transient failures don't cause message delivery to fail.How much does sending MMS cost compared to SMS?
MMS messages typically cost 3–10× more than SMS, depending on your Sinch plan and destination country. US domestic MMS costs approximately $0.02–$0.04 per message, while SMS costs $0.005–$0.01. International rates vary significantly by country. Check your Sinch dashboard under "Billing" → "Pricing" for exact rates, and consider implementing cost tracking in your application to monitor spending.
How do you track MMS delivery status and receipts?
Enable delivery reports by setting
delivery_report: "FULL"in your batch payload and providing acallback_urlwhere Sinch sends status updates. Implement a webhook endpoint to receive delivery notifications with statuses:Delivered,Failed,Expired, orRejected. Store batch IDs returned from Sinch API responses and use the/batches/{batchId}GET endpoint to poll message status programmatically.Can you test MMS sending in sandbox or development mode?
Sinch doesn't offer a dedicated sandbox mode for MMS. For development testing, provision a low-cost phone number and send test messages to your own devices. Keep file sizes minimal during testing to reduce costs. Implement feature flags to disable actual MMS sending in local development, returning mock success responses instead. Use environment variables to toggle between production and test modes.