

Select New registration. On the Register an application page, set the values as follows:


Click on Register. On the next page, copy the value of the Application (client) ID and Directory (tenant) ID and save them, you will need that later.


Select Add a permission. On the Request API permissions page, select Microsoft Graph.



Select Application permissions and then select:
Mail.Read
Mail.ReadWrite
Mail.Send

Click on Add permissions
Select Grant admin consent for org and click on the Yes button in the consent dialog.


Under Manage, click on Certificates & Secrets from the left-hand navigation pane.

Select New Client Secret, add a small short description and select Add.



Copy the value of the newly added client secret and save it, as you will need it later.
For New Deployments - The admin of Office 365 needs to perform Step 1 to Step 12
For Existing Sites - If the application is already registered in their tenant, they need to follow Step 5 to Step1