Privacy oriented mail solution
I was looking at JMAP RFC(https://datatracker.ietf.org/wg/jmap/about/) and other things related to it. Suddenly I found out about DMTP & DMAP protocol which is privacy oriented replacement for SMTP & IMAP. In fact Snowden used it to protect his mail communication where Lavabit was the provider and developer of this protocol. In fact the fate of Lavabit was previously discussed in LET multiple times.
Looks like they have an opensourced version of their server which is Magma.