Is there a way to disable the possibility to join externals (i.e. people outside my O365 tenant) the private meetings scheduled via Outlook button via 'Join Teams meeting' URL? I was looking for something within the settings, but only thing I found is to disable the private meetings at all which is not desided.
At the moment, no, as the default policy allows external users to join. They cannot start a meeting however, and someone from the company needs to admit them from the lobby. But we will soon be able to assign custom policies for Teams meetings as well, so stay tuned.