Hi Dsdeep,
I am also confused about your exact requirement. But if you have to inform everyone, then write it in the 'Circular' form. It can be structured like this:
Circular
To All Employees,
This is to inform you all that Management has decided that from now on, no employee will be allowed to take any type of leave on Monday. In extreme urgent cases, approval from the concerned HOD is required for leave on Monday. Prior intimation to the HR Department is necessary.
If you have any queries, please contact the undersigned.
Regards,