Microsoft Outlook Delegation Error–Cannot Activate Send-On-Behalf-Of List

If you received this error when trying to add a delegate to a mailbox, then you might want to check the permission of the SELF account of the mailbox which you want to add the delegate.

For example, Mary tries to add Peter as a delegate to have access to her mailbox and Mary received the above error when trying to do so.

So I will need to open Mary’s AD account, go to the Security tab and select the SELF account. Give the SELF account the Write and Write Personal Information permissions. Restart Mary’s Outlook and try again.