That being said. It looks like an amazing product. As a long time Arch Linux user this is very pleasing.
(Possible over-paranoid ideas include refusing port 25 smtp connections that wont negotiate a secured connection in response to a STARTLLS command, and possibly blacklisting mail originating from any of the 8 known PRISIM participants. I like the _idea_ of ensuring none of my mail arrives from known-intercepted sources, but reality dictates otherwise since way too many of the people I really do want to communicate with are exclusively using gmail/yahoo for email - or worse still, have migrated largely to Facebook messaging instead of email)
Also emails from personal servers don't have issues in my experience -- the only thing is that you need to do it right. The major webmail providers each have their own specific rules before they accept mail from unknown servers. Provided that you do those right, there isn't much of an issue. arkOS intends to implement these as default.