title: Nodemailer error: Cannot use 'in' operator to search for 'contentTransferEncoding'
body: <p>I'm trying to send a <strong>POST</strong> request from <strong><em>Unity to my web service endpoint in Node.js</em></strong>; I'm able to send emails without adding any attachments. But, when I try to send an array of attachments I always get this error.</p>
  
  <p><strong>Error</strong>: Cannot use 'in' operator to search for 'contentTransferEncoding' in [{filename: 'test.txt', contentType: 'text/plain', content: 'Hello World!', contentTransferEncoding: 'quoted-printable'}]</p>
  
  <p>I also tried to send a <strong>POST</strong> request from <strong>Postman</strong> but I get same error.</p>