Description of problem: Microsoft has announced that Office365 will deprecate basic authentication in favor of OAUTH: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basic-authentication-exchange-online This makes it impossible in its current state for users to use Office365 as an email relay, as cyrus-sasl has no method of supporting OAUTH2 authentication mechanism. There is a third-party plugin that does though but it's not currently packaged in Fedora: https://github.com/moriyoshi/cyrus-sasl-xoauth2
I made a copr repo with this package for now: https://copr.fedorainfracloud.org/coprs/jjelen/cyrus-sasl-xoauth2/ If it will work for you, we can move on to submit it as an official Fedora package or to epel
This was done some time ago. We did sasl-xoauth2 package though as we got reports that this is working better for our customers: https://github.com/tarickb/sasl-xoauth2 The package is no awailable in Fedora and EPEL8/9: https://src.fedoraproject.org/rpms/sasl-xoauth2 Closing as done.