Difficult, very difficult on deed. As with most corporate and whize collar crime, the investigation rate is extremely low. That being said, worker councils and unions. The former has to involved in these things, if the exist. The latter pushes for the former.

That is valid for Germany.

There really is none. A smart company would work with the 4 eyes principle though (still no guarantee).

However, if a company does find an unrelated e-mail they want to use against you (which is what most people fear), that makes them liable.