The idea was being contemplated by senior management here - one day during
which we would not use internal email. External email from clients would,
of course, have to be taken care of. As the post office admin, I was asked
if there was a way to accomplish this system-wide: block internal
correspondence but allow that to and from outside.

I couldn't help them on the system-wide enforcement thing, but offered to
ignore my internal email for the rest of the week as a test of the idea.