A user agent is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent. It is used by web browsers to identify themselves to web servers when making requests for content. This information can be used by web servers to deliver content that is tailored to the specific browser or device being used.

 

 

In Mailpro Application we use it for statistics purposes. You can see the Operating system and the browser(email agent for your subscribers.

 

 

This is what we find most in our own Mailpro Database according to millions of email opened per week:

 

Desktop User-Agent

 

Mobile User-Agent