When using Symantec Protection Engine (SPE) with the ICAP protocol, it responds to a scan request with
ICAP/1.0 505 ICAP version not supported. A packet capture of the scan requests shows a version other than 1.0 was used, for example:
REQMOD /symcscanreq-av-url ICAP/0.1
SPE only supports ICAP/1.0. Any other version of ICAP will cause it to respond with this error.
Work with the developer of your ICAP connector to troubleshoot why it is sending an unsupported ICAP request.
The following are situations that have caused connectors to send unsupported requests: