On the road to perfection First off  it's open source and you can build your own app from source files hosted on GitHub. Secondly  its a 'proper' email client with non of the useless bells and whistles you see on other email clients (looking at you Gmail). Lastly  as of version 5.2  it now supports PGP/MIME (need the OpenKeyChain). Gets better with each update.
January 02 2017