- You have a hybrid deployment of Microsoft Exchange Online in Microsoft Office 365 pre-upgrade and in your on-premises Microsoft Exchange Server environment.
- An Office 365 pre-upgrade user sends a meeting request in Microsoft Outlook that includes an on-premises conference room.
- The meeting request is accepted and the room is booked.
In this scenario, the user doesn't receive an "Accepted" email message from the room mailbox.
This issue occurs if messages that are sent from Office 365 pre-upgrade users to on-premises users aren't processed as internal messages.