Stop a Request from Being Forwarded in Outlook or the Outlook Web App

Stopping a meeting request from being forwarded is as simple as flipping a single setting before you send out the request.

In the full Outlook client, with an open meeting request, switch to the “Meeting” tab. Click the “Response Option” button and then click the “Allow Forwarding” toggle on the drop-down to turn it off (it’s on by default).

In the Outlook Web App, make sure you have a meeting request open and at least one attendee added. Click the “Attendees” cog and then click the “Allow Forwarding” toggle to turn it off for this meeting.

Unfortunately, there’s no way to have the “Allow Forwarding” option turned off by default. You have to turn it off each time you create a new request.

So What Happens If Someone Tries to Forward My Meeting Request?

Three things can happen when someone tries to forward a message on which you’ve turned off the “Allow Forwarding” option:

If your attendee is using the same version of Outlook as you (and if they work for the same company it’s very likely they are), then they won’t be given the option to forward the meeting request.
If they’re on an older version of Outlook, then they’ll be able to forward the meeting request, but Microsoft Exchange will block the delivery and send your attendee an “undeliverable” message.
If they’re using a non-Microsoft email system, like Gmail, then they’ll be able to forward the meeting request without any restrictions. This is because third-party systems are under no obligations to respect Microsoft’s “do not forward” flag. In the future it’s possible they will start to respect it (this is often a “you scratch my back, and I’ll scratch yours” situation, where someone like Google wants Outlook to respect a Gmail-specific flag, so a deal is done), but it’s also entirely possible that no system apart from Outlook will ever respect the flag.

Still, as long as you’re setting up meetings with people in your organization, this should work fine.

Source: https://www.howtogeek.com/366868/how-to-stop-someone-forwarding-a-meeting-request-in-outlook/