Outlook
Copy the below code. In Outlook paste it when inserting an image, use the drop down and select Link to File. Don't forget to change the 'CHANGEME' text to the name of your email!
https://www.google-analytics.com/collect?v=1&tid=UA-56773869-16&cid=12345678-9101-1121-3141-516171819202&t=event&ec=email&ea=open&dp=/email/CHANGEME&cn=email-campaign&cm=email
Stripo
Copy the below code. In Stripo paste it into the code editor section just below the <body> tag. Don't forget to change the 'CHANGEME' text to the name of your email!
<img src="https://www.google-analytics.com/collect?v=1&tid=UA-56773869-16&cid=12345678-9101-1121-3141-516171819202&t=event&ec=email&ea=open&dp=/email/CHANGEME&cn=email-campaign&cm=email">