John Works for a Company That Provides Computers and Access

John works for a company that provides computers and access to a service provider that provides access to the Internet,as well as an e-mail address for all employees.While at work,John often accesses the e-mail account that he uses at home.John's employer would like to access John's e-mail to see if he is using company time for personal purposes.Which of the following is true?

A) The company must get a search warrant before it can access any of John's stored e-mail.
B) The company can have access to e-mail stored at John's work e-mail address, but not that stored at the e-mail address he usually accesses from home.
C) The company can have access to e-mail stored at either location if the e-mail at the address he accesses from home was sent or received during John's time at work.
D) The company cannot access any of John's stored e-mail unless it obtains the assistance of law enforcement personnel and obtains a search warrant.
E) The company cannot access any of John's stored e-mail and would not have grounds for a search warrant.