How to delegate Mailbox Permissions?
The Mailbox Delegation feature allows you to assign or remove permissions (Full Access, Send As and Send On Behalf) for the selected users on selected Mailboxes.
Perform the following steps to delegate mailbox permissions:
Select Office 365 Manager from the available vertical tabs. Then from left side of the application, select Mailbox Permissions and then click on Mailbox Delegation.
On selecting "Mailbox Delegation", a pop - up window is displayed as shown below:
 

     
  • Select users/groups along with the Mailboxes and Click on the Next button to proceed.

     
To grant permission, use Grant Mailbox Permissions option and set Full Access, Send As and Send On Behalf from available option and Click on Apply button.
 

     
To remove permission, which was set earlier use Remove Mailbox Permissions option and Click on Apply button.