"You don't have to check it while you are on vacation. You can actually ignore it."
You don't _have_ to, but you can.
This is Europe.
There _is_ no unpaid overtime!
If people check their mail during vacation, they are working, and they have to be paid and their vacation is still due an they can sue the company when they leave (or not) to get payment for the missed holidays or weekends.
Same thing if you get sick or injured during a holiday, the days don't count as holiday but as sick days, even if you stay there at the beach bar with a cast for 4 or 5 weeks. (although you can't drink alcohol, since this can hinder a speedy recovery)
The vacation days are still due.
Also, people with a security/dangerous job have to be alert and cannot have worked _anything_ 8 hours before the shift, if case of an accident or other misfortune, the company would be liable.
"So why delete what could be important communication? Just deal with it when you are back in the office."
If it's really important, the vacation guy is replaced during his absence and the replacement handles the email.
If that's not the case, it's not an important job, even if the tenant thinks it is.