So it's come to my attention that many of you do not, in fact, have local copies of your email, relying solely on your cloud providers not to lock you out?

That's crazy to me. I have meticulously exported and reimported my IMAP mailboxes every time I switched provider, and keep local copies in a Maildir that goes back all the way to 2002.

Not only does this allow me to use powerful tools like mu, but I'm also not at the mercy of $TECH_COMPANY.