Re: Did the company make this policy known to everyone?
Yes, and perhaps put a few hints in the warning that the two perpetrators would recognise, just to make sure they got the message.
Mind you, I'm not subtle so it would probably have gone something like:
"Please remember that the email system is provided by $COMPANY for company business only, not so you can arrange affairs on company time. Please also remember that IT have access to all your emails, especially the ones you don't address correctly and we'd really rather not have to read your home made porn anymore."