Again, it depends on individual agreements. If the employee is not allowed to use his work company mail for private stuff, he has no reasonable expectation of p

Again, it depends on individual agreements. If the employee is not allowed to use his work company mail for private stuff, he has no reasonable expectation of privacy that goes beyond obvious cases. Like, for example, if your wife sends you a mail with the subject "here are my nudes!", your employer isn't allowed to access the content.