I personally don't, but many do. But it doesn't matter, my employer isn't legally allowed to read my emails, unless it's a sort of an emergency. My vacation, weekend, short sick leave and things like do not qualify. And even then, if the criteria is met, it's illegal to read anything else than strictly work related things out of my box.

We even have a form where people leaving the company sign permission that their mailbox can be accessed by their team leader and without signature we're not allowed to grant permissions to anyone, unless legal department is on the case and terms for privacy breach are met.