Because I’d like a firewall-proof interface, and want to dispense with andrew. I’ve installed uw-mailutils on andrew, for the mailutils program (also alpine, just because), and ran mailutil append INBOX '{imap.gmail.com/ssl/novalidate-cert/user=aguido.davis@gmail.com}' to transfer my inbox over. The horatio@computer.org alias now points at aguido.davis@gmail.com, there is a .forward in ~horatio on andrew, and the Google mail account now sends as horatio@computer.org, after verification.

Eventually I gave up on trying to move my archive folders by that method, and wired up mutt on andrew to IMAP on gmail more or less along these lines, with some context filled in from the mutt project’s IMAP notes. Saving from one folder to another fails less often, and it’s far easier to recover. The magic folders, incidentally, are visible as subfolders of [Gmail] on the server imap.gmail.com, port 993. The non-magic folders lie directly on the root; the inbox is the root.