Today i am going to show when, how and why we need to give "Delegated Email Approver" security role to the system administrator to approve email for active mailbox.
Suppose you have a requirement to enable Dynamics 365 App for Outlook to the Dynamics 365 user, for that you need to approve the email for that user..
As a system administrator you login into Dynamics 365 Customer Engagement and Advanced Settings
> Administration > Email Configuration
> Click on the Mailbox
Then you can see active mailboxes, select the mailbox you want to approve as you can see below screenshot and highlighted, click on the "Approve Email"
This role is only assign by either Global Administrator or Exchange Administrators only, system administrator can't assign Delegated Email Approver" security role by himself or herself.
So Global Admin should assign the Delegated Email Approver" security role to the system admin to perform the " Approve email" on Dynamics 365 to continue with the configuration of Dynamics 365 App for Outlook.
I hope this helps.
Malla Reddy {aka @UK365GUY }