Apple Mail on MacBook Pro fails to connect with Exchange (com.apple.accounts error 3)

Hello, I've been using the Apple Mail app on my MacBook Pro (Tahoe 26.2), iPhone and iPad to access mail from my hosted Exchange account. This has been working fine for a long time, until this week mail stopped working on the Mac only. iPhone and iPad still work fine. The authentication flow proceeds all the way to the MFA push on to Microsoft Authenticator, then fails with "The operation couldn’t be completed. (com.apple.accounts error 3.)". Logs on Exchange (falsely) suggest the password did not match. Logging on with a browser using the exact same credentials works fine. I've tried deleting and re-adding the account either as an Exchange account, or with just the email address, and the result is the same. I've even tried generating an app password on the back end, same result. I am suspecting this has to do tightening some security protocols on the back end. Has anyone else experienced this, and is there a workaround/solution? TIA.