Retail License
This type of license is only binding to your Operating System, so it's advisable to do image backup of your Operating System after activation, in case your OS crashes in the future
Overview of Microsoft Exchange Server Features
The ability to use "up to 48 processor cores and 256GB of RAM."
Support for solid-state drives, enabling improved e-mail search.
A Dynamic Database Cache feature that provides "more memory to active database copies."
International e-mail (EAI/IDN) routing support.