...
Client Id
Client Secret
Optionally Private Key, for Client Credential Authentication
Tenant Id
...
Click Save.
Authorize FlexDeploy
In order to authorize, you should login to http://outlook.com as the user you wish to authorize as first. Otherwise, especially if you are using SSO, it is likely that you will be authorizing as the wrong user. The idea is that when you click authorize, it will ask you who to login as, and you will select (or type) the same user that you have in the imap user / smtp user box that you are authorizing. You may need to use an incognito tab or guest window if your network signs you in automatically.
After populating the necessary fields, click either the Authorize or Re-Authorize buttons. At this point you will be re-directed to Microsoft to authorize FlexDeploy as the same user that you have in the imap user / smtp user box that you are authorizing. If everything is successful you should be redirected back to this page.
If you are ready, click the Authorize button.
Connecting a FlexDeploy account to a Microsoft Graph Application
Navigate to System Settings → Email Settings and use the page Configuring Graph OAuth - Microsoft Office 365 to configure it.