The Mouth of Sauron

[Balin999]

Quite true. One of the reasons that Sauron probably used the Mouth at all was to remain distanced from his troops [...]

That is a convincing point of view. But, I'll repeat my theory here: Sauron could not talk to living men. (At least after he had lost the ring.)
So, he needed someone to communicate with his troops/ anyone who had business with him.
Again, this may be wrong, but I can't remember any scene in LotR where Sauron talks openly. Any views on that?