I have just started to use an email client (Windows 10, Thunderbird) only in order to keep an archive of messages against the day any of my several historic and current free webmail providers delete my accounts for lack of use.
All my email is in plaintext but I want local copies of messages, and the local archive, to be encrypted. Preferably searchable too, but that is not totally necessary.
I am happy to ditch Thunderbird for a client that could do this.
I need IMAP because POP3 only finds the Inbox folder on webmail accounts. The client should also be password-protected to secure my email. I want to get to the state where nobody accessing my computer can read my email or impersonate me, or find out my email addresses, but email is still automatically saved locally.
Are there any solutions I can implement for free?