var esendex = require('esendex')({
  username: 'you@yourdomain.com',
  password: 'secure password'
});

esendex.inbox.update({ id: '8a6cae14-9bce-4195-830b-bd55e1c1ffef', read: false }, function (err) {
  if (err) return console.log(err);
  console.log('Marked message as unread!');
});