title: Sending email to multiple recipients via express-mailer issue
body: <p>I'm creating a simple send mail function using <strong>nodejs</strong>. the emails are handled by the <strong>express-mailer</strong> module</p>
  
  <p>Below is a section of my <strong>app.js</strong></p>
  
  <pre><code>var express = require('express');
  var app = express();
  var mailer = require('express-mailer');
  // view engine setup
  app.set('views', path.join(__dirname, 'views'));
  app.set('view engine', 'jade');
  
  mailer.extend(app, {
      from: 'no-reply@example.com',
      host: 'smtp.gmail.com',
      secureConnection: true,
      port: 465,
      transportMethod: 'SMTP',
      auth: {
          user: 'mymail@gmail.com',
          pass: 'mygmailpass'
      }
  });
  
  app.mailer.send('email', {
      to: 'test75@gmail.com,test4@gmail.com,test21@gmail.com',
      subject: 'Password reset', // REQUIRED. 
      body: 'Your Password is set to xxxxx. Please log in back.,',
      otherProperty: 'Other Property'
  }, function(err) {
      if (err) {
  
          console.log(err);
  
          return;
      }
      console.log('mail sent');
  });
  </code></pre>
  
  <p>and this is my email template, <strong>email.jade</strong></p>
  
  <pre><code>doctype html
  html
    head
      meta(http-equiv = 'Content-Type', content = 'text/html; charset=UTF-8')
      title= subject
      body
        p
          =body
  </code></pre>
  
  <p>the above app works well, the emails are fired to the recipient(s). issue is when there are more than one recipient, this is an image of how the individual recipient receives the email:</p>
  
  <p><a href="https://i.stack.imgur.com/GR2uf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GR2uf.png" alt="enter image description here"></a></p>
  
  <p>notice on the above image how when the recipient receives the email, they can view all the other recipients who have also received the same email. what is causing this behavior and how can it be avoided?</p>