It will be hard to make Mailpile user-friendly when you have to install it yourself on your own cloud server. But particularly with the end of free Google Apps accounts, I wonder if there is an opportunity here, either as something end-users can install themselves or as something mom-and-pop shared hosting companies can offer instead of their current always-awful webmail. Maybe you could even build a business around an encrypted webmail tool you license to shared hosting providers.

If Mailpile or someone else is going to be self-installed, I'd love to see it built as PHP. (Looks like Python right now.) As much as I refuse to develop in PHP, that seems like the only way to make installation as easy and ubiquitous as Wordpress, which should be the goal.

(I realize that either Mailpile or my own suggestion---or anything hosted on someone else's hardware---is vulnerable to someone reading the data right out of RAM, but it seems like their goal is to evade snooping not by building a 100% secure system, but by making it easy and affordable for everyone to have their own email server, so that government surveillance has too many targets to be practical.)