title: Using signature to track email open with GA per email (not campaign)
body: <p>I would like to track email opens with Google Analytics using the signature in the email. There are quite some articles on this (e.g. <a href="https://stackoverflow.com/questions/4456592/tracking-email-opens-in-google-analytics">Tracking email opens in Google Analytics</a>) however as I understand it, these would only provide a general open rate per campaign. E.g. if I send 100 emails, it would send me the % of emails that were opened.</p>
  
  <p>What I would like to know, is what exact email has been opened. Let's say I send 4 emails, I would like to know which of these 4 emails was opened. Since all examples use a general GA campaign, this is not covered in these solutions (right?).</p>
  
  <p>I guess in some way, it would have to pass a unique ID with the pixel upon adding the signature. Potentially through the Scripts API? Any ideas on how this could be done? I doesn't have to be through the signature, I just figured this would be easiest. If there are other ways of doing this when an email is created or sent, then this would also be very helpful.</p>
  
  <p>EDIT:
  Requirement to the solution would be that I install or connect it once, and from there on it will add this unique ID automatically (or upon adding the signature).</p>
  
  <p>EDIT 2:
  I came up with a potential solution, however I am not confident this is best practice. I could use the Google Apps Admin SDK to set a signature for a user, which includes a unique tracking code. As soon as an email with this tracking code is sent, I could update the signature again with a new tracking code. It's the best I've come up with so far. Maybe it sparks some other ideas...</p>
  
  <p>EDIT 3:
  In response to the campaign suggestions: the idea is that this tracker should be easy to add when I send a normal email from GMail. Therefore solution like SendGrid are not suitable, cause I would habe to leave my normal email client for it.</p>