Color icons
For the most part airmail works great. The one gripe I have is that the color icons in the inbox in the iOS app are completely different than those in OSX on my Mac. Like website icons and such are the same, but when there just the green circle with an F in it on my phone, its Pink on my Mac or something like that. Make it harder to skim through and find something quickly that you would otherwise recognize in one OS from the other.
HayfireDrummer about
Airmail - Your Mail With You, v1.6.4