I just pushed to master (and thus the nightly packages, tonight), a lot of improvements to how Mailpile does OpenPGP encryption. In particular, all of the Autocrypt spec except for the Setup Message should now be supported - modulo bugs, of course.
There were also a bunch of fixes to the key discovery in general, and WKD (Web Key Directory) in particular.
Just to document this somewhere - our Autocrypt support is “compatible” with legacy GnuPG usage in that it will not override a key that is already marked as trusted on your local key chain. So if you’ve been using the web of trust and/or manually verifying keys, Autocrypt won’t step on your toes. But it will happily import (and update) keys for anyone else.
Please report any and all issues you find, this is a big change and a big step towards where I want to be for 1.0.