It's not an alternative if you are looking for a web based interface, but I wrote gpgmda[1] (which integrates the alot MUA) to move myself off gmail when the TO

It's not an alternative if you are looking for a web based interface, but I wrote gpgmda[1] (which integrates the alot MUA) to move myself off gmail when the TOS changed a few years ago. [1] https://github.com/jakeogh/gpgmda https://github.com/jakeogh/gpgmda