Dare to turn off the Outlook Reading Pane.
I tried it - by accident - and now I can go through my emails so much faster. Even though I always could delete stuff that wasn't interesting by looking at the title, the Reading Pane encouraged me to take a look at it, read a bit of it, just to make sure I'm not deleting anything important.
Now I either open the email in full, and it better be worth it, or I delete it without ever having laid my eyes on its content.
It's a brave move, but so far I'm very happy with my decision. I dare you to try this for a whole day. 🙂