I use Streak to track emails. Knowing an email has been opened is a great relief. Especially those crucial job or project proposal applications. Its not fool proof as it works by including a tiny pixel image which is requested from a server when the email is opened. So if images are turned off or other settings to prevent that data exchange are in place... well they don't want to be tracked! If all is well the following data is available. A notification pops up too when the email is opened. Very reassuring.
Check it out I love it - https://www.streak.com/
Now on the surface it's quite complicated and when I was tracking down the info to blog this, the "CRM in your inbox" tagline made me grimace slightly. I realised that I only use the free bit, the inbox power tools so if you want to explore the CRM stuff go for it, but if like me you just need the email power tools. Yippee!
Install the extension, reboot Chrome, reopen Gmail and look for the orange Streak icon top right in the Gmail window. If it's there its running. Thats it. Next email you send a green eye should appear in the far right of email's data line.