encrypting incoming emails

[streaps]

This is just an enhancement idea, me thinking out loud. Unfortunately I don't know the internals of the Protonmail web client and I cannot contribute any usable code to neutron.

How could incomming emails be encrypted? Maybe by an LMTP server that sits between Postfix and Dovecot?

World --smtp--> Postfix --lmtp--> Neutron encryption --lmtp--> Dovecot local delivery

Does this make any sense? Could it work?

[streaps]

Another idea would be that the web client encrypts unencrypted emails via IMAP.

[emersion]

The first solution can work pretty well. I prefer it over the second one since messages would be stored encrypted from the start.

[alexis-]

The most elegant implementation I could find (using Dovecot), was this one : https://perot.me/encrypt-specific-incoming-emails-using-dovecot-and-sieve

You may also be interested with these:
https://0xacab.org/riseuplabs/trees
https://www.grepular.com/Automatically_Encrypting_all_Incoming_Email
http://kacangbawang.com/encrypting-stored-email-with-postfix/

Although I am uncertain how this is related to neutron mail.