I stumbled across this article on alternative email clients for iOS (none of which you can set as your default email client, because of the dumb limitations of iOS) and this just leaped out at me:
Email on the move needs to be fast. It needs to arrive quickly and notify you promptly so that you’re always up to date. There needs to be easy and swift ways to deal with the email when you’re on the go and can’t stop to devote an hour to cleaning up your inbox.
No, no, no. You do not need to be notified quickly. You do not need to be up to date on your email when you are doing something else, like walking your dog, or buying groceries, or sitting unwinding and reading a book. All this notification and attention stealing does is turn you into one of those people stumbling around on a sidewalk or in a shop staring at a screen and bumping into things. And also, sending incoherent emails to people, because only half your brain is engaged in the task.
Email is a wonderful thing, except when you fall prey to the delusion that it requires immediate responses. If someone needs you right now, they can call you. Or text you. If they are emailing you, they are sending you a high speed letter, and when you should read your mail when you have some time to actually do that.
The ideal email client defaults to notifications being turned off and has no unread count badge. This is true whether the email client is on your phone, your computer, or (god help you) your watch.
Constant interruption is the enemy. Turn off your notifications, stop checking your phone compulsively, and free yourself to actually use your mind.