ProxySG DOES NOT support 'fail_open' for ICAP REQMOD in the following cases:
1. Any FTP request on which:
- ICAP connection is disrupted during data transfer.
- ICAP server returns error 4xx or 5xx.
2. An HTTP request larger than 8K on which:
- ICAP connection is disrupted during data transfer.
- ICAP server returns error 4xx or 5xx.
In these cases an ICAP error is returned to the client.