Leonov says the "Triage" method comes from the Napoleonic wars when the chief surgeon came up with a method to separate wounded soldiers into three categories: those who are going to die quickly no matter what you do, those who will live no matter what you do, and those who will make a significant improvement if they receive immediate attention.
In the corporate world, the Triage method encourages workers to separate their email into three categories: those that should quickly be deleted in bulk, those that you can deal with quickly, and those that need to be worked on when you return from vacation.
Leonov says the majority of the emails will belong in the "immediately delete" category, while the minority of the emails will belong in the "requires attention upon return" category. The middle category of emails — those that can be dealt with on the fly — can either be forwarded to a coworker or can be snoozed to reappear in your inbox at a more convenient time.
To fit into the middle category, Leonov says the reply should take less than two minutes — but he recommends restricting it to 30 seconds or less while on vacation.