Microsoft Rolls Out Block for Calendar Forwarding

A New Way to Block Forwarding of Important Meeting Requests

Microsoft has started to roll out a new feature in Exchange Online, OWA, and Outlook 2016 (click to run) to stop people forwarding meetings when meeting organizers don’t want them to do so. You know the scenario: someone sets up an interesting meeting with a well-chosen list of attendees to figure out how to solve a problem and next thing you know, 50 people turn up to meet in an overcrowded room because some of the invited attendees decided to pass on the meeting notification to their colleagues.

By default, meetings can be forwarded, but now organizers have a new option in Outlook 2016 and OWA (see below) to disable forwarding of their meetings.

CalendarAllowForwarding
Outlook 2016 option to stop a meeting being forwarded
CalendarAllowForwarding3
Turning forwarding off in OWA

When an attendee opens the meeting request, the client disables the forward option.

CalendarAllowForwarding2
Ooops! The option to forward the meeting is grayed out.

Of course, an attendee could create their own meeting request and cut and paste the meeting details into that request and send it to whomever they like, but that’s probably too much work. This fix cuts out casual forwarding, and that’s what it is intended to do.

Supported Clients

The new feature is now available in OWA, Outlook 2016 (click to run version 1808 – I see it in client build 10730.20102). Microsoft says that it is coming to Outlook for Mac soon. It is not available in Outlook 2016 MSI clients. Only users with Exchange Online mailboxes can blocking the forwarding of meetings.

Lots of Unsupported Clients

Obviously, there’s lots of unsupported clients in use today. An unsupported client doesn’t have the user interface to disable meeting forwarding or to stop someone forwarding a meeting that the organizer has blocked. It therefore follows that people who receive blocked meetings might try to forward them.

To make the block more effective, Microsoft has included a check in the code that submits messages to the Exchange transport service to validate that someone has the right to forward a meeting request. To have that right, the submitter must be the meeting organizer or a delegate of the meeting organizer. Users assigned editor access to the organizer’s calendar can also forward meetings, but only if they are granted that right under the new calendar sharing model. Those with editor rights granted under the old model can’t forward meetings.

If the submitter has the right to forward a meeting, transport accepts and processes the message. If they don’t, transport politely declines the message and issues a non-delivery notification.

This block is built into Exchange 2016 (latest cumulative update), Exchange 2019, and Exchange Online, so anyone with a mailbox connected to one of those servers respects blocks set on meeting forwarding. If someone using an older Exchange server or a non-Exchange server receives a meeting request, they can anything they want with it because the block isn’t available.

The formal Microsoft support article is available online. We cover calendar sharing in Chapter 6 of Office 365 for IT Pros. And if you’re at Microsoft Ignite, check out session BRK3146 to discover all the new stuff that’s happening in Outlook calendaring.

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