The rooms are possible to book for users within the tenant, i.e.,
user1 may schedule a meeting in
room1, but I now want to make them available also for some external users, let's call it
I've read a ton of guides such as this and this and this about this, and they all pretty much say the same thing; it's the
ProcessExternalMeetingMessages property that allows this. If it's enabled, by default anyone should be able to send a scheduling request to the resource's mailbox.
So from PowerShell I've done
> Set-CalendarProcessing -Identity Room1 -ProcessExternalMeetingMessages $true
I've verified that the change is in effect:
> Get-CalendarProcessing -Identity Room1 | fl ProcessExternalMeetingMessages
ProcessExternalMeetingMessages : True
I've also published the calendar:
Set-MailboxCalendarFolder Room1:\Calendar -PublishEnabled $true
This gives me a public URL in which the calendar is viewable with free/busy information.
Furthermore, I've added my user as a delegate to the resource so that I can view its mailbox, verified that "Everyone" is allowed to book the resource, verified that there are no custom transport rules preventing e-mail delivery to the resource, and even explicitly shared the calendar with my external user
Still, when trying to book a meeting with the resource as the location, there's never any response. The event is not added to the room calendar, there is no accept/decline answer sent back to the booking user, and there is no invitation e-mail in the resource's mailbox. It's clear that external meeting requests are not processed.
If I book the room from
[email protected], it instantly responds with an accept, and in the resource's mailbox the received invitation and the sent response is visible.
I feel like I've turned every stone now, trying to understand why this room cannot be scheduled. Every guide says that if
true, by default anyone may schedule that resource, but I cannot even do it after explicitly publishing and sharing the calendar with my particular user.
How could I debug this further? Is there any global setting that could override the
ProcessExternalMeetingMessages settings, such as a policy that blocks or restricts external messages on a higher level?