Create a `.env` file in your project's root directory. Add your Infobip API key (INFOBIP_API_KEY), base URL (INFOBIP_BASE_URL), and MMS-enabled sender number (INFOBIP_SENDER_NUMBER). Load these values in your code using the `dotenv` library, ensuring `.env` is added to `.gitignore`.

Express creates the web server and API endpoints that clients (like Postman or a frontend app) can use to send requests to trigger MMS messages. It handles routing, middleware (like validation), and interacts with the Infobip service to send the messages.

Implement `try...catch` blocks around Infobip SDK calls to handle potential errors during the MMS sending process. Log detailed error information for debugging but avoid exposing sensitive details in production responses. Return appropriate HTTP status codes (like 500 for server errors) and user-friendly error messages to the client.

Retry sending if you encounter transient network issues or specific HTTP status codes like 429 (Too Many Requests) from Infobip. Use libraries like `p-retry` to simplify this process and configure backoff strategies, but avoid retrying permanent errors like incorrect API keys or invalid recipient numbers.

In your route validation, use `express-validator`'s `isURL` function to ensure media URLs are valid HTTP or HTTPS links. This prevents accidentally using invalid URLs and can also help reduce the risk of security issues like Server-Side Request Forgery (SSRF) attacks.

Aim for a total MMS size (text + media) under 300KB-600KB for optimal compatibility across carriers. Infobip often recommends under 300KB but may support up to 1MB depending on the carrier and region. Always verify media size before sending if possible.

Apple devices (iOS) have inconsistent support for SMIL (Synchronized Multimedia Integration Language), which controls the presentation of MMS content. It's recommended to avoid using SMIL and instead rely on the order of elements in the message payload's content array for sequencing text and media.

Use the Infobip API and Node.js SDK along with Express. Create an Express app, integrate the Infobip SDK, define an API endpoint, and handle MMS requests using the SDK's methods for sending multimedia messages. This setup allows you to send MMS messages programmatically from your Node.js application.

It's a library (`@infobip-api/sdk`) that simplifies interaction with the Infobip API from Node.js applications. It provides methods for various communication channels, including MMS, making it easier to send multimedia messages without complex API calls.

Dotenv helps manage environment variables, allowing you to store sensitive API keys (INFOBIP_API_KEY, INFOBIP_BASE_URL) and other configuration in a `.env` file. This file should be excluded from version control (add it to `.gitignore`) for security reasons. The application loads these values at runtime without exposing them directly in the code.

Use `express-validator` middleware functions *before* your route handlers (controllers). This ensures that data sent to your API endpoints is validated and sanitized according to your defined rules, preventing issues with invalid data and improving security.

The example code provided sends to one recipient at a time. For group MMS, refer to the Infobip API documentation for the correct payload structure or endpoint. Group messaging often depends on sender number type and carrier rules.

You need an Infobip account, API key, base URL, and an MMS-enabled sender number. Install Node.js, npm/yarn, and have a basic understanding of JavaScript/Node.js and asynchronous programming.

Construct the MMS payload as a JSON object with fields like 'from', 'to', 'subject', and 'content'. The 'content' field is an array, where each item has a 'type' and relevant data based on the type (e.g., 'TEXT' with a 'text' field, or 'IMAGE' with a 'url' field). Verify against the Infobip API documentation for the correct structure and required fields.

Use a PaaS (like Heroku, Render, or Vercel) if it supports MMS functionality, or deploy using containerization (Docker, Kubernetes) or VMs. Configure environment variables on your chosen platform without committing `.env` to Git, ensure your package.json has the necessary scripts, and consider using a Procfile for deployment.