How to Track Gmail Messages with Google Analytics modified for Universal Analytics tracking. You will need to copy this spreadsheet http://goo.gl/Tk1nR8 and then open Tools > Script Editor to replace the existing code or simply add the /* Universal Analytics Tracking */ part

track_email_opens.js

/* 

    Email Tracking with Google Analytics
    ====================================
    
    Written by Amit Agarwal on 09/24/2013
    
    Tutorial: http://labnol.org/?p=8082
    YouTube : http://youtu.be/9T_EqwQnZY0
    Support : http://twitter.com/labnol
    
    Modified for Universal Analytics tracking


*/


function onOpen() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var menu = [ 
    {name: "Initialize", functionName: "reset"},
    {name: "Send Mail", functionName: "launch"}
    ];  
  ss.addMenu("Email Tracker", menu);
  ss.toast("Please click the Email Tracker menu above to continue..", "", 5);
}

function reset() {  
  return;
}


function launch() {
  var threads = GmailApp.search('in:draft', 0, 10);
  if (threads.length === 0) {
    Browser.msgBox("We found no templates in Gmail. Please write a draft message in your Gmail mailbox to continue.");
    return;
  }
  var myapp = UiApp.createApplication().setTitle('Email Tracker').setHeight(160).setWidth(300);
  var top_panel = myapp.createFlowPanel();   
  top_panel.add(myapp.createLabel("Please select a draft message"));
  var lb = myapp.createListBox(false).setWidth(250).setName('templates').addItem("Select draft...").setVisibleItemCount(1);
  
  for (var i = 0; i < threads.length; i++) {
   lb.addItem((i+1)+'- '+threads[i].getFirstMessageSubject().substr(0, 40));
  }

  top_panel.add(lb);
//  top_panel.add(myapp.createLabel("").setHeight(10));
//  top_panel.add(myapp.createLabel("Please enter your Analytics Profile ID"));
  var name_box = myapp.createTextBox().setName("name").setWidth(250);
  top_panel.add(name_box);  
  top_panel.add(myapp.createLabel("").setHeight(5));
  var ok_btn = myapp.createButton("Send Mail"); 
  top_panel.add(ok_btn);
  myapp.add(top_panel);
  
  var handler = myapp.createServerClickHandler('sendMail').addCallbackElement(lb).addCallbackElement(name_box);
  ok_btn.addClickHandler(handler);
  
  SpreadsheetApp.getActiveSpreadsheet().show(myapp);
}

function sendMail(e) {
  
  var draft = GmailApp.search("in:drafts")[(parseInt(e.parameter.templates.substr(0, 2))-1)].getMessages()[0];
  var email = draft.getBody();
  var attachments = draft.getAttachments();
  var to = draft.getTo();
  var cc = draft.getCc();
  var bcc = draft.getBcc();
  var subject = draft.getSubject();
  var id = draft.getId();

  var regMessageId = new RegExp(id, "g");
  
  if (email.match(regMessageId) != null) {
    var inlineImages = {};
    var nbrOfImg = email.match(regMessageId).length;
    var imgVars = email.match(/<img[^>]+>/g);
    var imgToReplace = [];
    for (var i = 0; i < imgVars.length; i++) {
      if (imgVars[i].search(regMessageId) != -1) {
        var id = imgVars[i].match(/Inline\simages?\s(\d)/);
        imgToReplace.push([parseInt(id[1]), imgVars[i]]);
      }
    }
    imgToReplace.sort(function (a, b) {
      return a[0] - b[0];
    });
    for (var i = 0; i < imgToReplace.length; i++) {
      var attId = (attachments.length - nbrOfImg) + i;
      var title = 'inlineImages' + i;
      inlineImages[title] = attachments[attId].copyBlob().setName(title);
      attachments.splice(attId, 1);
      var newImg = imgToReplace[i][1].replace(/src="[^\"]+\"/, "src=\"cid:" + title + "\"");
      email = email.replace(imgToReplace[i][1], newImg);
    }
  }
  
  var trackingGIF = getTrackingGIF(e.parameter.name, to, subject);
  
  email = email + "<img src='" + trackingGIF + "' width='1' height='1'/>";
  Logger.log(email)
  
  GmailApp.sendEmail(to, subject, email, {attachments: attachments, htmlBody: email, cc: cc, bcc: bcc, inlineImages: inlineImages});      
    
  var app = UiApp.getActiveApplication();
  app.close();
  return app;
}

function getTrackingGIF(account, email, subject) {
  
  try {
    
    /* Google Analytics Account ID like UA-1234-56 */    
    /* I will put it in by hand instead of typing all the type */
    var utmac = "UA-XXXX-Y";
    
    /* Random ID to prevent browser caching */    
    var utmn = (Math.round((new Date()).getTime()/1000)).toString();    
    
    /* Relative path of the Web Page to be tracked */
    // var utmp = "/inbox/" + email.replace("@", "."); 
    
    /* Universal Analytics Tracking */
     var request_UA = "https://www.google-analytics.com/collect?"
     +"v=1" + "&"
     +"tid=" + utmac +"&"
     +"cid=1" + "&" 
     +"t=event" + "&"
     +"ec=email" + "&"
     +"ea=open" + "&"
     +"el=" + subject + "&"
     +"cs=email" + "&"
     +"cm=email" + "&" ;
      // +"CD1=" + email;     // store the email as a Custom Dimension. BEWARE : Not fine by GA!
    
    return request_UA; 
    
  }
  catch(e) {
    Logger.log(e.toString());
  }
}