Symantec Endpoint Protection (SEP) and ProxySG device(s) are in the same environment.
Integrate the use of SEP and ProxySG.
Symantec announced that SEP can be integrated with ProxySG.
To integrate SEP with ProxySG, a Content Analysis System (CAS) running 2.1 or later or Advanced Secure Gateway (ASG) running 6.7.2.1 is required.
The ProxySG and\or ASG must be configured to send client IP via ICAP to CAS. The CAS must be configured with Sandboxing and SEP services.
Please see this documentation for details:
Integrate Proxy with CAS: Manually Configure an ICAP Service on the ProxySG
Integrate CAS wit SEPM: Integrate with Symantec Endpoint Protection Manager
CAS with ProxySG integration guidelines