To use Microsoft Graph on Office 365, requires setup in Office 365 to allow Azure permissions for API.

• Login to office.com as Administrator
• Open Admin Center

• In Admin center Select Azure Active Directory

• Select Azure Active Directory
• App Registrations
  • Select New registration
  • Enter in Name for example Sage 300 Email

• At this point the overview will show Application (Client) ID and Directory (tenant) ID.

• The only remaining requirement is a Secret.
• Select Add a certificate and secrets.
• New client secret, Add a client secret.
• Be sure to copy the Secret Value, this must be done when the page is first created. Values are then not viewable.

• Select API Permissions
  • Add a permission
  • Select Microsoft Graph
• Select Delegated permission for signed-in user
  • Scroll down list to Mail
  • Select Mail.Read
  • Add permissions
• Select Add permission, Microsoft Graph, Application Permissions
• Select Mail.Send
• Select Grand Admin Consent to allow. 

With the above information, you are now able to fill out the Graph service requirements.  Application, Directory, and Secret Value.