Re: Devils advocate.
My viewpoint is that there's no reason for the admin to be reading those emails in the first place - just bounce them. I'm guessing he set this up as a way of snooping, rather than to be helpful.
Anyway, they aren't sharing trade secrets with the competition, the emails aren't illegal. He knows nothing of the details - this pair may have left their spouses which makes the email completely innocent, for example.
It's not for him to judge. I was once told by a colleague that he gets sucked off every time he goes to Amsterdam. I didn't feel the need to tell anybody, especially his wife. None of my business.