HELP : I've replaced reals IP by this :
- 192.168.0.21 --> my LAN IP from where I test. (Full right on SOPHOS for ALL WEB/LAN)
- 100.0.0.1 --> my public static IP. The SOPHOS and IIS are behind this IP.
- private.mydomain.com --> the url that I test. I test with http:// and https://
note. The certificate is autosigned by my IIS. I know that and trust it. Error for certificate is not important. Certificate was added on the SOPHOS.

HTTP request of my site. Error is normal cause I force SSL use in website configuration.

2014:03:13-11:54:47 sophos-1 reverseproxy: [Thu Mar 13 11:54:47.819978 2014] [cookie:warn] [pid 23566:tid 3804621680] [client 192.168.0.21:62607] Dropping cookie '__utma' from request due to missing/invalid signature
2014:03:13-11:54:47 sophos-1 reverseproxy: [Thu Mar 13 11:54:47.820118 2014] [cookie:warn] [pid 23566:tid 3804621680] [client 192.168.0.21:62607] Dropping cookie '__utmz' from request due to missing/invalid signature
2014:03:13-11:54:47 sophos-1 reverseproxy: srcip="192.168.0.21" localip="100.0.0.1" size="2096" user="-" host="192.168.0.21" method="GET" statuscode="403" reason="-" extra="-" time="16576" url="/" server="private.mydomain.com" referer="-" cookie="-" set-cookie="-"
2014:03:13-11:54:48 sophos-1 reverseproxy: [Thu Mar 13 11:54:48.013727 2014] [cookie:warn] [pid 23566:tid 3804621680] [client 192.168.0.21:62607] Dropping cookie '__utma' from request due to missing/invalid signature
2014:03:13-11:54:48 sophos-1 reverseproxy: [Thu Mar 13 11:54:48.013909 2014] [cookie:warn] [pid 23566:tid 3804621680] [client 192.168.0.21:62607] Dropping cookie '__utmz' from request due to missing/invalid signature
2014:03:13-11:54:48 sophos-1 reverseproxy: srcip="192.168.0.21" localip="100.0.0.1" size="2086" user="-" host="192.168.0.21" method="GET" statuscode="403" reason="-" extra="-" time="12702" url="/favicon.ico" server="private.mydomain.com" referer="-" cookie="-" set-cookie="-"


HTTPS request of my site

2014:03:13-11:56:05 sophos-1 reverseproxy: [Thu Mar 13 11:56:05.778301 2014] [url_hardening:error] [pid 23566:tid 3888548720] [client 192.168.0.21:62641] Hostname in HTTP request (private.mydomain.com) does not match the server name (srvdc.lea.local)
2014:03:13-11:56:05 sophos-1 reverseproxy: srcip="192.168.0.21" localip="100.0.0.1" size="202" user="-" host="192.168.0.21" method="GET" statuscode="403" reason="-" extra="-" time="892" url="/" server="srvdc.lea.local" referer="-" cookie="__utma=125257754.1800519950.1394123532.1394123532.1394178517.2; __utmz=125257754.1394123532.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)" set-cookie="-"
2014:03:13-11:56:05 sophos-1 reverseproxy: [Thu Mar 13 11:56:05.875484 2014] [url_hardening:error] [pid 23566:tid 3888548720] [client 192.168.0.21:62641] Hostname in HTTP request (private.mydomain.com) does not match the server name (srvdc.lea.local)
2014:03:13-11:56:05 sophos-1 reverseproxy: srcip="192.168.0.21" localip="100.0.0.1" size="213" user="-" host="192.168.0.21" method="GET" statuscode="403" reason="-" extra="-" time="729" url="/favicon.ico" server="srvdc.lea.local" referer="-" cookie="__utma=125257754.1800519950.1394123532.1394123532.1394178517.2; __utmz=125257754.1394123532.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)" set-cookie="-"