I woke up from my trance and bailed on my disjointed bricolage of Fastmail->Gmail->Mimestream. Cobbling various pieces together just so I can use a single mail client on my Mac seemed…shortsighted. Mimestream is nice, but not that nice, you know?
So I’m back in MailMate and/or Mu4e. Oh, and sometimes Apple Mail. But I’m thinking about switching back to notmuch from Mu4e. Now that I say it, I’m not sure this is any better :). At least I’m not relying on Gmail now, I guess.