In revision 9957 (Remove HTTP/1.1 sent to clients), NTLM passthrough was broken for Outlook clients, which require 1.1 to work properly. When receiving 1.0, Outlook closes the connection (which breaks NTLM since it requires a continued session). Version 3.1.2 works fine for these clients. Note this is likely the cause of bug 3141.
In 2.7, the http_port option 'http11' allowed forcing version 1.1 to clients. That was removed when 3.1 defaulted to 1.1, but when this change was reverted, the http11 option was not added back. Squid 3.2 latest works fine, since 1.1 is now the default again. Can we either a) make 1.1 the default in 3.1 again b) add back the 'http11' option Thanks, Phil