title: SendGrid - Event Responses with Custom parameters
body: <p>We are implementing email system for mass mailing. </p>
  
  <p>As per our requirements we are going to use send grid as a third party email service providers.
  The individual email activity track using post event responses from send grid to figure out percentage of spam, clicks, double clicks and bounces. </p>
  
  <p>But while receiving event responses from send grid, we cannot differentiate multiple responses on same email address. </p>
  
  <p>Shall it be possible that we will send some unique id with each email header sent through send grid and receive that unique email id in event responses?</p>