code: function buildEmail(envelope, data) {
    return simpleParser(data)
      .then(function(parsedEmail) {
        const sender    = envelope.mailFrom.address;
        const receivers = envelope.rcptTo
          .map(recipient => [ recipient.address, true ])
          .reduce(tupleToObject, {});
  
        const headers   = [ ... parsedEmail.headers ]
          .map(readHeader)
          .reduce(tupleToObject, {});
  
        const email     = {
          sender,
          receivers,
          data,
          headers,
          body:      parsedEmail.text,
          html:      parsedEmail.html,
          attachments:      parsedEmail.attachments
        };
  
        return email;
      });
  }
docs: Resolves to the email object handlers receive.