We are on Office 356 Wave 15.
The PA to our CEO wants to be able to "Forward" meeting requests that have been placed in the CEO's calendar by an organiser outside our company. When she tries to do this she get the undeliverable message below, with the "To" user being the user she was forwarding the mail to.
The PA has Owner permissions on the calendar and Full Access on the mailbox. As well as send As permissions.