We had a very unusual experience happen today:
This is her normal behavior for creating meetings that are not specific to a Team or Teams/Channel. How could this have happened?
@PeterRising Thank you and I agree this should not have happened. None of the non-invited guests received the meeting request. The meeting chat just appeared in their chat list. One person attempted to join the meeting, but was not allowed to. Another person sent me a screenshot that had a message that she couldn't send a message because she was not a member of the chat. Very strange. I will take your advice and contact Microsoft support. I just wanted to try to troubleshoot it before doing so. Thank you!
@LBumgarner Hello, by any chance this was a recurring meeting invite being reused with another set of users? That would explain the behavior at least, meaning why the non-invited users had the meeting chat activated. Other than that I have to agree with what @PeterRising said. As for the meeting and lobby behavior they are controlled by either the individual meetings options or assigned meeting/messaging policies and the guest settings as well.
@bec064 Thank you for your input. This was not a recurring meeting invite that was re-used. Some of the users who received the meeting chat would not normally be part of meetings. For example, one of the users who that showed up in the list was our IT service account. It has a M365 account, but would never be invited to a meeting. Others were users who don't normally participate in meetings, other than their own departments or committees, but there's not a common denominator that I can find.