Greg Mason

I figured out the issue.  The email integration will also throw this error if an Office 365 username is different than their primary email address.  O365 username and primary email address must match.  So, if my O365 username is gmason@zendesk.com and my primary email address is GregMason@zendesk.com, the integration will fail with "Cannot Authenticate."

I've made sure settings for the mailbox are correct.  Settings for the organization are correct.  What other reasons would this error pop up?