Can't speak for author but I use mbsync to keep an old Gmail account but self host the emails from my own server where everything is encrypted at rest. It synci

Can't speak for author but I use mbsync to keep an old Gmail account but self host the emails from my own server where everything is encrypted at rest. It syncing the emails to one place allows me to manage the 6 accounts most of which are work related through the one dovecot/roundcube interface.