We have just tried scheduling a load of webinars over the next few months where we have external experts presenting to our organisation. Turns out external users cant join if you are hosting a private webinar BUT they can present if you invite them to a live event?! Why do I have to open my webinar up to the world to allow an external user to present to my company?
Microsoft recently changed the language used on the Webinar creation form. They changed Private to "Your Organization" and kept Public the same and also added some language clarifying what each setting does.
And choosing the Public option does not open the event up to everyone. It only allows people outside of your organization to join. It's only open to the world if you post your link to the world.