Email Tracking
I do not use tracking all the time, just occasionally for emails which I want to know that the recipient has read.
My preferred tracking agent is GETNOTIFY, a simple sign-up program that is not installed, but once you are on their register is activated by adding ".getnotify.com" to the recipients email address. This addition does not show on the recipients email.
When the email is opened you get an email alert from GETNOTIFY.
https://www.getnotify.com/