Identification of user roles and system functions

1.User roles:
a)Administrator
b)User

2.System functions:
-Sending messages
-Receiving messages
-Loging in to the system
-Creating messages
-Writing messages
-Reading messages
-Saving draft
-Delete draft
-Replaying to messeges
-Viewing history
-Creating groups of recipients
-Viewing drafts history
-Viewing messages history
-Sending a raport with summary