Again, worked there, not how it works. As I said it doesnt matter if its "signed" and "encrypted".. **all** external emails need admin approval, there is no signing and encrypting to bypass this.
You seem to be missing the main point... no one, not even the president has the ability to email everyone. The system is designed to prevent this exact thing. So there intentionally is no account that has any way, signed or not, to do this.. it **must** be passed on by department heads through these gateways manually, this is an intentional security feature and there is no account that can bypass it
Who specifically controls the list is ultimately determined by the head of the department, as are the specific procedures for determining what is passed on or not. Typically it's someone close to the leadership like a secretary who approves those requests on company wide lists.
Doc Freemo 
@chris @adam
You seem to be missing the main point... no one, not even the president has the ability to email everyone. The system is designed to prevent this exact thing. So there intentionally is no account that has any way, signed or not, to do this.. it **must** be passed on by department heads through these gateways manually, this is an intentional security feature and there is no account that can bypass it
The government is compartmentalized as a feature.