Now that they've disabled basic authentication for email connection protocols, Microsoft is doing the same for the Autodiscover service. This makes sense. There's no point in allowing basic authentication for Autodiscover when clients can't use basic authentication to connect. Microsoft will therefore turn off basic authentication for Autodiscover as it removes basic authentication for protocols like POP3, EAS, IMAP4, EWS, and MAPI.
The great remove basic authentication from Exchange Online project is rapidly approaching the October 1 date when Microsoft will start removing support for basic authentication for seven email connectivity protocols. We've known about this date for well over a year, but some organizations need a little extra time to be ready. Microsoft is offering a one-time three-month extension to January 1, 2023. After that, they're going to proceed with the final termination.