SkipDev you can log the error happening inside server/index.js file at line number 48, inside the catch block like this:

} catch (error) {
  console.log('error', error);
  res.status(500).send({
    success: false,
    message: 'Something went wrong. Try again later'
  });
}

so now when you send email, you will be able to know exact reason for the error.