serverDownSendMail.js

const isReachable = require('is-reachable'),
nodemailer = require('nodemailer');

function checkStats() {
isReachable('api.example.com').then(reachable => {
    if (reachable === true) {
        console.log('Server is up');
    } else {
        console.log('Server is down');
        const transporter = nodemailer.createTransport({
            service: 'gmail',
            auth: {
                user: 'yourmail@gmail.com',
                pass: 'yourpassword'
            }
        });
        const mailOptions = {
            from: 'yourmail@gmail.com',
            to: 'recipient@example.com',
            subject: 'Server stats',
            html: '<b>Server is down</b>'
        };

        transporter.sendMail(mailOptions, function(error, info) {
            if (error) {
                console.log('Message failure: ' + error);
            } else {
                console.log('Message sent: ' + info.response);
            }
        });
    }
});
setTimeout(checkStats, 5000);
}

checkStats();