[CptMouse]

Airmail is quite good, and AFAIK you can turn off some of its many features. http://airmailapp.com/ (hint: You can use it for free if you use the beta version)

I was a huge fan of Sparrow (like you, I used it long after the updates stopped), then Airmail and Mailbox, but now I simply use the Gmail web app. I follow the zero inbox method strictly, so I only need to read/archive/reply/search emails, and it does a decent job at it (except for search where it's best in class), while being simple and non-confusing.