Node.js dummy email queue, when SMTP fails

EmailQueue.js

/**
                           |--------|
                     /--X--| SMTP 1 |
                    /   ^  |--------|
                   /    \--- Retry with next provider
|----------------|/        |--------|         |------------------|
|   Mail         | ---X--> | SMTP 2 |      /->|  ^_^ Happy user  |
|----------------|\   ^    |--------|     /   |------------------|
                   \  \--- Retry         /
                    \      |--------|   /
                     \---->| SMTP 3 |--/
                           |--------|
                           
// EXMAPLE

EmailQueue.sendEmail({        
    to: 'test@example.com',
    subject: 'You\'ve got an email!',
    text: 'Plain text message',
    html: '<h1>HTML</h1><p>Styled message</p>'
}, (err) => console.log('email not send', err))                           
*/

import { Email } from 'meteor/email';
import nodemailer from 'nodemailer';

const EMAIL_SERVERS = {    
  'email1@exmaple.com':'smtps://email1@example.com:pass@example.com',
  'email2@exmaple.com':'smtps://email2@example.com:pass@example.com',   
  'email3@exmaple.com':'smtps://email3@example.com:pass@example.com'
};

// we need transports 
const transports = [];

for (let email in EMAIL_SERVERS) {
    let transport = nodemailer.createTransport(EMAIL_SERVERS[email]);
    transport.from = email;
    transports.push(transport);
};

function sendEmailFromTransport(transportsArr, emailData, callback) {

  //if all emails fail track this event
  if (transportsArr.length == 0) {
      if (typeof callback == 'function') {
          callback(emailData);
      }           
      return;
  }
  
  //remove the first transporter from the array
  let transporter = transportsArr.shift();
  
  //change from so it is same as sending transporter, to bypass SPAM 
  emailData.from = transporter.from;
  
  transporter.sendMail(emailData, (err) => {
    // transporter failed now trying next one;
    // timeout is used for performance 
    if (err) {
      Meteor.setTimeout(() => {
        sendEmailFromTransport(transportsArr, emailData, callback);
      }, 500);
    }     
  });
}