I'm looking for a guide, or just a list of tools with some advice. I want to protect the emails stored on the server-side (in a Courier-IMAP server).
A basic flowchart to illustrate the idea.
[Unencrypted mail comes in] | [Encryption with public key] | [Saved to file] | [Client downloads file] | [Decryption with private key]
I use Thunderbird. I am sure it can be done, it's a pretty streightforward process. May be an other program should be inseted between the mail client and the server, or an extension has to be used. May be the original message file has to be an attachment to a wrapper message (to be flawlessly handleled by the mail client). May be an add-on can help.
I'm open to any ideas how to solve this.