Sandra shared this one with me today, and neither of us had thought about using Undo in this fashion. But it works really well for getting an email back that you inadvertently sent to the Deleted Items folder (assuming you use Undo right after you did the delete).
Here is my Inbox with a couple of items in the Today category:
If I hover over the right side of the red Inbox entry, you’ll see the red X for deleting that item. I’ll go ahead and click on it:
As expected, it disappears from the Inbox. But by clicking the Undo arrow in the upper left corner of the screen, I can reverse the effects of that deletion, and get the email back in my Inbox:
And there it is again after the Undo:
The reason I really like this tip is that I often go to delete an item, and a new item comes in RIGHT before l click the red X, meaning that I end up deleting the wrong email. With the Undo trick, I can easily get the email back without going into the Deleted Items folder to try and figure out what I deleted.