const http = require("https");

const options = {
  "method": "POST",
  "hostname": "control.msg91.com",
  "port": null,
  "path": "/api/v5/email/send",
  "headers": {
    "Authkey": "<authkey>",
    "accept": "application/json",
    "content-type": "application/json"
  }
};

const req = http.request(options, function (res) {
  const chunks = [];

  res.on("data", function (chunk) {
    chunks.push(chunk);
  });

  res.on("end", function () {
    const body = Buffer.concat(chunks);
    console.log(body.toString());
  });
});

req.write(JSON.stringify({
  to: [{name: 'Mark', email: '[email protected]'}],
  from: {name: 'Joe', email: '[email protected]'},
  cc: [{email: '[email protected]'}, {email: '[email protected]'}],
  bcc: [{email: '[email protected]'}, {email: '[email protected]'}],
  domain: 'The domain which you have registered with us. We sign DKIM with this domain.',
  mail_type_id: '1 for Transactional, 2 for Notificational, 3 for Promotional - Default is 3',
  in_reply_to: 'If the current mail is reply of any mail then that mail Message ID.',
  reply_to: [{email: '[email protected]'}, {email: '[email protected]'}],
  attachments: [
    {filePath: 'Public path for file.', fileName: 'File Name'},
    {
      file: 'File in Data URI format data:content/type;base64,<data>.',
      fileName: 'File Name'
    }
  ],
  template_id: 'YOUR_UNIQUE_TEMPLATE_NAME',
  variables: {VAR1: 'VAR1 VALUE', VAR2: 'VAR2 VALUE'}
}));
req.end();

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://control.msg91.com/api/v5/email/send",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "\n{\"to\":[{\"name\":\"Mark\",\"email\":\"[email protected]\"}],\"from\":{\"name\":\"Joe\",\"email\":\"[email protected]\"},\"cc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"bcc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"domain\":\"The domain which you have registered with us. We sign DKIM with this domain.\",\"mail_type_id\":\"1 for Transactional, 2 for Notificational, 3 for Promotional - Default is 3\",\"in_reply_to\":\"If the current mail is reply of any mail then that mail Message ID.\",\"reply_to\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"attachments\":[{\"filePath\":\"Public path for file.\",\"fileName\":\"File Name\"},{\"file\":\"File in Data URI format data:content/type;base64,<data>.\",\"fileName\":\"File Name\"}],\"template_id\":\"YOUR_UNIQUE_TEMPLATE_NAME\",\"variables\":{\"VAR1\":\"VAR1 VALUE\",\"VAR2\":\"VAR2 VALUE\"}}\n",
  CURLOPT_HTTPHEADER => [
    "Authkey: <authkey>",
    "accept: application/json",
    "content-type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

require 'uri'
require 'net/http'
require 'openssl'

url = URI("https://control.msg91.com/api/v5/email/send")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_NONE

request = Net::HTTP::Post.new(url)
request["Authkey"] = '<authkey>'
request["accept"] = 'application/json'
request["content-type"] = 'application/json'
request.body = "\n{\"to\":[{\"name\":\"Mark\",\"email\":\"[email protected]\"}],\"from\":{\"name\":\"Joe\",\"email\":\"[email protected]\"},\"cc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"bcc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"domain\":\"The domain which you have registered with us. We sign DKIM with this domain.\",\"mail_type_id\":\"1 for Transactional, 2 for Notificational, 3 for Promotional - Default is 3\",\"in_reply_to\":\"If the current mail is reply of any mail then that mail Message ID.\",\"reply_to\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"attachments\":[{\"filePath\":\"Public path for file.\",\"fileName\":\"File Name\"},{\"file\":\"File in Data URI format data:content/type;base64,<data>.\",\"fileName\":\"File Name\"}],\"template_id\":\"YOUR_UNIQUE_TEMPLATE_NAME\",\"variables\":{\"VAR1\":\"VAR1 VALUE\",\"VAR2\":\"VAR2 VALUE\"}}\n"

response = http.request(request)
puts response.read_body

import http.client

conn = http.client.HTTPSConnection("control.msg91.com")

payload = "\n{\"to\":[{\"name\":\"Mark\",\"email\":\"[email protected]\"}],\"from\":{\"name\":\"Joe\",\"email\":\"[email protected]\"},\"cc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"bcc\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"domain\":\"The domain which you have registered with us. We sign DKIM with this domain.\",\"mail_type_id\":\"1 for Transactional, 2 for Notificational, 3 for Promotional - Default is 3\",\"in_reply_to\":\"If the current mail is reply of any mail then that mail Message ID.\",\"reply_to\":[{\"email\":\"[email protected]\"},{\"email\":\"[email protected]\"}],\"attachments\":[{\"filePath\":\"Public path for file.\",\"fileName\":\"File Name\"},{\"file\":\"File in Data URI format data:content/type;base64,<data>.\",\"fileName\":\"File Name\"}],\"template_id\":\"YOUR_UNIQUE_TEMPLATE_NAME\",\"variables\":{\"VAR1\":\"VAR1 VALUE\",\"VAR2\":\"VAR2 VALUE\"}}\n"

headers = {
    'Authkey': "<authkey>",
    'accept': "application/json",
    'content-type': "application/json"
    }

conn.request("POST", "/api/v5/email/send", payload, headers)

res = conn.getresponse()
data = res.read()

print(data.decode("utf-8"))