Regarding revised Notice period for all current employees

Dear All,
What will the format for revised Notice Period intimation to currently working employees.Company wants to inform all employees about NP which is reduced from 30 days to 15 days.Please help me out in this.

Hi,
If the notice period clause is already mentioned in the Appointment letter, then please issue a separate letter to all employees referring their appointment letter date (Referring to your appointment letter dated__ clause of no_ stands revised as follows.......) and get signature in the duplicate copy.