For emails, here is my current simple backup setup. Of course, I’m also looking to do this without having to open Thunderbird, or I might have an old laptop running it. So, work-in-progress.

For the email accounts I want a backup, I set it to spew out POP3 without doing anything (don’t mark read or delete). I set up Thunderbird with that POP3. It has a backup copy of all the emails. I’ve had searchable emails since like 2004/2005, and I’ve occasionally replied to people and gotten back in touch with very old friends from the Internet.

I saw an open-source tool sometime back (I think, here on Hacker News) that backs up your IMAP mails with a nicely done interface. That would be nice to have.

Edit: Perhaps Bichon,[1] mentioned somewhere in the other comment threads[2] was the one.

1. https://github.com/rustmailer/bichon

2. https://news.ycombinator.com/item?id=46429250