Yeah that’s what I’m saying. Even if you’re not using one of the big providers there’s a good chance they’re going to be at least handing it on its way to your self-hosted inbox, and its contents are unencrypted while they’re handling it (unless you encrypt the contents yourself). So there’s not much benefit to self hosting email if your goal is to keep your data out of big tech’s hands (and if that is your goal, don’t send anything important with email)