After creating a new default throttling policy, will it apply all previous users also or only new users which will be created??

I am using exchange 2010. Have planned to create a new throttling policy and make it default with customize setting.

Will this be applied for only new users or old users also where already default exchange throttling policy applied.

I want only new users to be applied on this default, do not want any change for old users.

Arif