svbito

Mailpile has an interesting architecture to prevent this. But they are trusting the "server". Something you have to do if you want all the fancy functionality like indexing, search etc. You can encrypt your index, though. So unless the whole server gets compromised your data is still encrypted in a secure way.

As I see it, the JS gets downloaded from the untrusted server, encrypts data on the client and sends it to the server.

What makes it impossible for the untrusted server to serve malicious JavaScript? I can't think of a scenario where I could trust code I get from an untrusted party...

If you like to learn a lot about the internals of SMTP and mailservers in general and need/want a super reliable, fast and (if the setup is carefully crafted) secure mailserver - I like qmail.

My setup is qmail (SMTP) + vmailmgr + Dovecot (IMAP) and it was pretty easy to set up.

To start with qmail, I would recommend http://www.lifewithqmail.org/