Ive been using Airmail on iPhone for about a year now, but recently got an iPad Pro. Airmail is optimized for the new 10.5, and man is it fast. I really like all of the features, particularly the snooze, and follow up features.
I had a small issue with app, but when I emailed support they got back to be immediately, and they kept following up until we got it figured out. I was talking to Steven and Sarah, they were both awesome.
I would love to see Airmail include more contact management features, like the ability to connect social profiles to contacts in the app.
Overall, I think Airmail is the go to app for mail on iOS.
dasmart about Airmail - Your Mail With You, v1.6.7