Create a Next.js API route that interacts with the MessageBird Batch API. This route should handle recipient input, construct the API payload, make the request to MessageBird, and process the response. A frontend form can collect recipient numbers and the message body, then trigger this API route.

The MessageBird SMS Batch API is a service that allows you to send a single SMS message to multiple recipients in one API call. It's more efficient than sending individual messages and simplifies message management.

Next.js API routes offer a serverless function environment ideal for handling backend logic like interacting with external APIs such as MessageBird. They are easy to set up and manage, making integration straightforward.

Bulk SMS is beneficial when you need to send the same message to many recipients simultaneously, like for alerts, notifications, or marketing communications. This guide's implementation is specifically for sending one message to up to 50 recipients at once.

This guide's code handles a maximum of 50 recipients per API call. To send to more, you'll need to modify the API route to split the recipient list into chunks of 50 and make separate API calls for each chunk. This chunking logic is not included in the basic guide.

Store your API key in a `.env.local` file. Next.js loads these variables into `process.env` server-side. This file is included in `.gitignore` to prevent accidental commits of sensitive data. Never expose your API key in frontend code.

The `MESSAGEBIRD_ORIGINATOR` sets the sender ID that recipients see. It can be a phone number (E.164 format) or an alphanumeric string (up to 11 characters). Consult MessageBird documentation and country-specific regulations before using alphanumeric sender IDs, as restrictions often apply.

The provided code includes basic error handling and logging. For production, use a logging library like Pino or Winston for better tracking. MessageBird API responses should also be thoroughly checked for errors, and proper error responses returned to the client.

Phone numbers should use the international E.164 format (e.g., +14155552671). This format includes the '+' sign and country code, ensuring consistent and reliable message delivery. For production, use a dedicated library like `libphonenumber-js` to enforce and validate the format.

To get final delivery reports, you need to set a `reportUrl` in your MessageBird API request. This URL should point to an endpoint in your application that can handle MessageBird webhooks (DLR callbacks) and then update internal statuses.

For sending to large recipient lists (hundreds or thousands), the Batch API isn't the best approach due to the recipient limit per message. In production, consider using queues or a dedicated MessageBird product designed for large-scale messaging, and implement chunking in your API route to respect the recipient limit per API call (50 in this implementation).

Common issues include invalid API keys, incorrect sender IDs (MESSAGEBIRD_ORIGINATOR), and invalid recipient phone numbers. Always double-check these and consult MessageBird documentation for specific error codes.

The official MessageBird API documentation is the best resource for details on API usage, limits, webhooks, error codes, and other features. Refer to it throughout the integration process for the most up-to-date information.