System Keyring for use on corporate mail servers

[bcook]

SM 1.4.15, GPG V2.1, Apache 2, PHP 5

The SM site says that a feature of the GPG plugin is a system keyring for use on corporate mail servers.
However, I looked through the documentation and could not find anything else on the subject (I could have overlooked it-let me know).  

Does anyone know how to enable this feature-- the only thing I see now is an option for the system keyring?  

Any suggestions are greatly appreciated.