By looking at the error you show in the attached image, it seems that the proxy is trying to access a domain not allowed by the CoS.
You can check the allowed domains by the CoS with the following command :
Code:
zmprov gc YOURCOS | grep zimbraProxyAllowedDomains
If your webex domain is not allowed, you can add it with the following command :
Code:
zmprov mc YOURCOS +zimbraProxyAllowedDomains YOURDOMAIN