When you track an email, Mailbutler attaches an invisible pixel to your message. That pixel is tracked - meaning we will let you know whenever it is accessed. But because all your recipients receive the same email, they also receive the same pixel - this is why per recipient tracking is not available with the current technology.

 
Multiple recipient tracking is something we'd love to offer in Mailbutler and we will definitely be working on adding this in the future.
However, if you're using Mailbutler Business, you have the option to view Tracking Details (when, where and what device your email has been opened) which should give you a better insight to how each of your recipients is reading your email.
 

For instructions on how to use Mailbutler's Tracking feature, please visit the below articles.

Open Tracking in your email
How to view Tracking Details with Mailbutler?
How do I use Link Tracking to track my email links?

For general information on Tracking, check out our feature page.