Use a Third Party Applicaiton to send to CAS or ProxyAV
Symantec does not test and support any third party ICAP clients in conjunction with ProxyAV or CAS. The only supported ICAP client is ProxySG. Due to the fact that ProxyAV and CAS support standard ICAP (RFC 3507), third party ICAP clients that also support standard ICAP should work together with ProxyAV or CAS. In such a deployment, Symantec would still fully support any ProxyAV or CAS (software and hardware) related issues. However Symantec would not support any third party ICAP client related issues (configuration, troubleshooting, etc.).
As long as you agree with the above support conditions, you can deploy ProxyAV or CAS with a third party ICAP client.