The Inbox Window
Check email twice a day and stop losing the hours in between.
Email open in the background is not checking email. It is being interrupted every few minutes by a queue other people control.
Every check costs the reconstruction of whatever you were doing, and the cost is invisible because it does not feel like work. Batching into two fixed windows keeps the same total email time but removes most of the small context switches in between, which is plausibly a large part of where the day was going.
Pick two windows and put them in the calendar
Late morning and late afternoon works for most people. Not first thing, which hands your best hour to other people's requests.
Close the tab in between
Not minimise. Close. Anything visible gets checked, and notifications off is not enough on its own.
Tell the three people who need to know
Anyone who genuinely needs you fast gets a different channel. That is usually two or three people, not everyone.
Empty the window, then leave
Deal with what is there in the time you gave it. Perfection here costs more than the few things that wait until tomorrow.
Go deeper
What the paid version adds to this one.
How to negotiate this in a job where fast replies are expected
The reply templates that make a batched window fast enough to work
What to do with the first day, when the backlog is the problem
A filmed pair of windows on a real inbox