I was wondering if there is a way to encrypt emails that have already been received with PGP. There seem to be tools like IMAPCrypt, but I have yet to get it to work under Ubuntu.
I would hope there is some way to either encrypt saved emails over IMAP, or to maybe download them over POP3 and encrypt them locally with PGP. Ideally only the content and attachments of an email would be encrypted.
So far my own email provider only allows me to encrypt all unencrypted emails with my public key as soon as they are received.