[somerandomqaguy]

Not unusual but a little interesting that your boss is explicitly asking that you be available during holiday. And I don't think it's unreasonable for them to ask.

If I were you, I would see if you can work something out with your boss that's agreeable to both of you. Maybe it's fine just to glance at the emails for 5 or 10 minutes in the whenever time window is convenient, with no expectation of action until you actually are back to work. If that's no good enough (i.e. they want you explicitly looking at your emails for a set window) then try to see if there's some other form of acceptable recompense in exchange for you to be working on holiday, for example extra pay to compensate for the fact that your giving up some vacation time to do work.