Outlook App Authentication failing

[techgeek1776]

We are experiencing Outlook App authentication fails across our organization suddenly.

No changes have been made on our end. 

Is Microsoft having issues or is anybody else dealing with this 

[#2]

Has security defaults been applied to your Azure AD tenant , blocking legacy protocols?

[#3]

@techgeek1776 

It may be too late for my reply, btw, what kind of authentication are you using? (e.g. Exchange Active Sync)

How about OWA (Outlook Web App), working?