I like K-9 mail app the most as its now having lot of features but one thing which I am concerned about is my privacy, as now a days privacy is the major concern for every one.(My main concern is privacy and security).
How recently have you tried it? It got a major UI overhaul about a month ago, and it looks almost exactly like GMail now.
EDIT: I just noticed I’m on their BETA track in Google Play - not sure if that UI change hit the release version or not, yet.
Although it may be an interesting topic, the post is a re-post from reddit with SPAM URL, which I suggest the post should be deleted.