Email OAuth 2.0 Proxy <https://github.com/simonrob/email-oauth2-proxy>; mailctl <https://github.com/pdobsan/mailctl>; mutt_oauth2.py <https://gitlab.com/muttmua/mutt/-/blob/master/contrib/mutt_o...> (some suggestion that it might not always work these days?); pizauth <https://github.com/ltratt/pizauth>; oauth-helper-office-365 <https://github.com/ahrex/oauth-helper-office-365>. Disclaimer: I wrote pizauth and it's just about to move into the alpha stage.