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When an SMS or MMS arrives on your mycpaas number, mycpaas immediately sends an HTTP POST request to your configured webhook URL. Your server receives the message details, decides how to handle them, and can reply with a LaML XML response to send a message back to the sender.

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When this webhook fires

This webhook fires every time an inbound SMS or MMS is received on a mycpaas number. It fires once per message, immediately on receipt.

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Payload fields

mycpaas sends the following fields as application/x-www-form-urlencoded in the POST body:
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From
string
required
The phone number that sent the message, in E.164 format (e.g., +491234567890).
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To
string
required
Your mycpaas phone number that received the message, in E.164 format (e.g., +491098765432).
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Body
string
required
The text content of the message.
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MessageSid
string
required
A unique identifier for this message (e.g., SM123abc...). Use this to deduplicate retries.

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Raw POST payload example

POST /webhooks/sms HTTP/1.1
Host: your-server.example.com
Content-Type: application/x-www-form-urlencoded

From=%2B491234567890&To=%2B491098765432&Body=Hello&MessageSid=SM1234567890abcdef

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Responding with LaML XML

To send a reply back to the sender, return a LaML XML response with Content-Type: text/xml and HTTP 200. Wrap your reply text in <Response><Message>: 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Message>Thanks for your message</Message>
</Response>
If you don’t need to send a reply, return an empty <Response> or any HTTP 200 response with an empty body.

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Handler example

The following Express handler parses the inbound payload and replies with a confirmation message: 
import express from 'express';

const app = express();
app.use(express.urlencoded({ extended: false }));

app.post('/webhooks/sms', (req, res) => {
  const { From, To, Body, MessageSid } = req.body;

  console.log(`Inbound SMS from ${From} to ${To}: ${Body} (${MessageSid})`);

  // Reply with LaML XML
  res.set('Content-Type', 'text/xml');
  res.status(200).send(`<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Message>Thanks for your message</Message>
</Response>`);
});

app.listen(3000);
Your webhook endpoint must respond with HTTP 200 within a few seconds. If it times out or returns an error status, mycpaas may retry the delivery. Use the MessageSid field to detect and ignore duplicate requests.