In the thread https://community.sophos.com/products/unified-threat-management/astaroorg/f/75/t/63938 Ulmi mentioned that the logging has been improved for http proxy with failed ipv6 cases. However I get error messages if I make any changes to the proxy via webadmin. I don't have ipv6 enabled.
2012:03:29-16:15:27 gatekeeper httpproxy[5857]: id="0003" severity="info" sys="SecureWeb" sub="http" request="(nil)" function="parse_address" file="util.c" line="548" message="getaddrinfo: passthrough6.fw-notify.net: Name or service not known"
2012:03:29-16:15:27 gatekeeper httpproxy[5857]: id="0003" severity="info" sys="SecureWeb" sub="http" request="(nil)" function="confd_config_filter" file="confd-client.c" line="2633" message="failed to resolve passthrough6.fw-notify.net, using 2a01:198:200:680::8080"
Regards
Bill