To communicate a message to all the users in your organization, you can send a mass email to everyone at once.
From the customer view in https://admin.webex.com, go to Services.
Under Meeting, select Sites, choose your site, then select Configure Site.
Select Email All Hosts, write your message, then select Send.
In your message to all users, do not include any variables that are in the email templates for your Webex service.