Hi,
There is a way to globally verify email - our account rep sent us this information last year:
"If you do not want users to be required to very their email addresses individually, you will have the ability to verify the domain for site starting with 39.2. Any users with email belonging to the verified domain will not see the email verification or alert icon. For instructions on verifying the domain for your site please see this article."https://help.webex.com/en-us/zm8xff/Verify-an-Email-Domain-in-Cisco-Webex-Site-Administration
I used the domain verification and it worked well for us but I did need to have our Network IT dept. add the token generated on the Admin page to the DNS server for each of our email domains that we used.