To help make your organization more secure, you can block users from joining meetings that aren't within your organization.
When you block users from joining external meetings, they can't join meetings that are hosted from Webex sites outside of your organization. But you can allow users to join meetings on certain Webex sites, by adding those Webex sites to an approved list setting.
Before you begin
You must claim the domains of users that you want to block from joining external meetings. If users in your organization have a domain that hasn't been claimed, they can still join external meetings even if the setting is enabled.
From the customer view in https://admin.webex.com, go to Meeting and Settings.
Switch the toggle in the Block external meetings section to on.
Under Approved sites list for external meetings, enter a Webex site and click Add.