This is on a MEAN stack project on a VPS. Server OS: Ubuntu 20.04

Problem: Emails are getting sent using gmail or other SMTP credentials. But when a specific domain email credentials are used. The email doesn’t go.

The below is the mail config being used.

  "mailServerOptions": {
    "pool": true,
    "host": "xxx.xxx.xxx.xxx",
    "port": 465,
    "secure": true,
    "auth": {
      "user": "[email protected]",
      "pass": "xxxxxxx"
    },
    "tls":{
      "rejectUnauthorized":false
    }
  }

The sendEmail method:

async function sendEmail({ to, subject, html}) {
  const copyMailServerOptions = JSON.parse(JSON.stringify(config.mailServerOptions));
  const transporter = nodemailer.createTransport(copyMailServerOptions);
  let sendEmail = true;
  const xFrom = copyMailServerOptions.auth.user

  transporter.verify(function(error, success) {
    if (error) {
      sendEmail = false;
      console.log('email transporter error', error);
      throw 'email transporter error: ' + error
    } else {
      try{
        const result = transporter.sendMail({ from: xFrom, to, subject, html });
      } catch(error){
        console.log('transporter.sendMail to: ' + to + ' - Error: ' + error)
      }
    }
  });

}

Checked host IP address. Its correct.

I have tried

1. by removing port and secure properties from the above config object – email doesn’t go.
2. port: 587, secure: false – email doesn’t go.
3. using host: "mail.specificDomain.com" – email doesn’t go.
4. using another domain email credentials – email goes.
5. gmail options – email goes.

This config was being used in the past and it used to work a few months ago. Now needed to use these credentials again and realised it stopped working.

What could be possibly wrong?