One cost of moving out of Gmail so that Google isn't learning shit about you to use against you and others in harmful ways is that you no longer (probably) have infinite storage.
So, you have to have a mail client periodically download your mail so you don't run out of space on your mail service. Because I want this to all be automated and searchable, I ended up
installing offlineimap, mutt, and notmuch on my Raspberry Pi, then scheduling downloads and indexing.
Though, now that I think about it, maybe I should have just searched harder initially for a mail service with lots of storage? Oh, well. I'm happy with Fastmail otherwise.