Feature Request: Mailbox encryption / Dovecot MailCrypt plugin

[besendorf]

It would be a huge privacy gain for Excision-Mail if it supported user mailbox encryption. Dovecot offers a plugin called MailCrypt which provides this functionality. It offers two modes. Global keys and folder keys.
Global keys encrypt all mail accounts with the same key, this is useful when you want to save the mailboxes on a different server or Storage provider (Amazon S3, etc.).
Folder keys uses a different key for each folder (user mailbox) derived from the users IMAP password. This means administrators are unable to read users mails, which is a huge privacy gain but this is also a security gain, as an attacker who gained access to the mailboxes also cant decrypt the emails(unless he controls the server long enough that he intercepts IMAP passwords).
There is also a paper explaining mailbox encryption in detail and analyses the implications for performance. Unfortunatly its in German:
https://gitlab.com/bifi/mailboxencryption_thesis/-/blob/master/thesis.pdf

[epsilon-0]

@besendorf
This is possible to add but this doesn't give users privacy.
Unless the mail has been encrypted using a public key from the sender, any encryption that an admin does can be circumvented by the admin, by storing the email before encrypting it.
On the other hand, it is true that this would help stop an attacker getting admin access from reading the past emails, though new mails will not be secure. So there is a slight benefit.
I've though about doing this but this is not trivial to add.
Thankfully we now have all the features we need from a mail setup, with web mail and caldav, so I can think about adding this optionally ❤️
Fair warning, this might take time as I am quite busy with university.