From our understanding the depreciation of the Basic authentication should not affect LF appliance and devices like copiers scanners which are using the SMTP relay with Basic authentication frequently as well. The SMTP + Basic authentication should still work after the 1st October. Microsoft should not disable it in the tenants which are actively using it. LF appliance with its current postfix configuration does not support the oauth2 authorization and it is not planned in current 3.x versions. If Microsoft although accidentally disabled the basic SMTP authentication on the client submission accounts which are used by your LF servers then you should be able to explicitly re-enable it. If the basic authentication was completely disabled also for SMTP in future then you could easily reconfigure your LF relay settings to some another relay service like SMTP2Go.
