You need to know what the port requirements are for Mac clients to allow WSS traffic.
By default, the Mac firewall is not activated, but the administrator may have configured this differently. The Mac Operating System does not have an application-based firewall service. Ports must be opened directly unlike a Windows application firewall.
A Mac client, using WSS to communicate to the WSS cloud service, requires these outbound ports:
These ports need to be open for WSS traffic. The destination Data Center IP address will depend on the location of the Mac and the configuration of WSS.
For Datacenter locations please see https://knowledge.broadcom.com/external/article/167174/web-security-service-wss-ingress-and-egr.html
WSS IP/port and required protocols information:
https://techdocs.broadcom.