Except telling people to log off is a loser proposition. It will never work and makes the IT dept. look amateurish. There are cost-effective ways around the problem as described. Indeed, if PSTs are the issue, you stop using PSTs. I understand they are not the nightmare they used to be, but OSTs and storing data on the server are a better option (even hard caps on email storage - although I don’t like those). Even being up to date on OS and email software will help to work around this.
I am out of IT now, and I never log out during the week. End of day, I three finger salute and lock the machine. My email is server stored and offloaded to archive files for retention policy purposes, all in the background.