If you publicize that you can read the messages, no problem.

I had a boss that liked to spy in the private messages of the employees without their knowledge. A bunch of interns started to privately create offensive nicknames for a fat employee. They didn't used the name in public. The read and started to use to use the nicknames in his conversation.

Well, this guy also publish jobs ads for our old tech stack with a false company name to see if any of his employees were applying.

Talk to me about lack of ethic.