When you attempt to manage the permissions of another account's (User/NetID, Service Account, or Resource) calendar, you receive one of the following errors:
Important: Even though you received this error, the action (adding or removing permissions) you performed was completed successfully. It's only that the user you added/deleted did not receive an email notifying them of this change.
This action requires that you have the ability to either 'send as' or 'send on behalf of' the account. At this time, you only have full mailbox permissions to this account.
If you want users to receive the email notification automatically, grant the account that is managing these permissions 'delegate' rights to the calendar of the account. Note: If you are granting these permissions to a service account, it must be viewable in the Global Address List). Delegate rights provide the user with 'editor' and 'send on behalf of' rights.