This one is going to be hard to swallow, perhaps.
I could give you the answer in one short sentence.
In fact, I will. But I don't feel I can do it without preamble, or else you may be tempted to take it merely as a joke, or dismiss it out right.
So please understand me when I say my advice on this subject is quite serious. And please believe me when I also say that the answer to your e-mail problem is deceptively simple.
You will, no doubt be skeptical about my solution. All I ask is that you are at least open to it.
I'm not asking you to believe me, I am simply asking you to suspend your disbelief until you have tried it.
Okay, here is how to do your e-mail in just 30 minutes a day…
When you open your e-mail program, set a timer for 30 minutes, and when the timer expires, you are done with e-mail for the day.
That's it. There's nothing else.
The timer will force you to be efficient, to keep your responses short, and to respond only to e-mails worthy of a response. The timer will force you to discard all junk mail, all entertaining-but-unproductive e-mail, and it will force you to be ruthless about what you give your attention to.
The timer is the only discipline you need.