Grant "Trust for Delegation" to the proxy machine

Thunderstone Search Appliance Manual

Grant "Trust for Delegation" to the proxy machine

The machine that runs the Proxy Module & authProxy must be marked as trusted for delegation by the Active Directory domain controller. This is necessary for the proxy to automatically "pass along" the users' authentication to the searched web sites.

On the domain controller, go to Start - Programs - Administrative Tools - Active Directory Users and Computers.
Choose Computers on the left.
Locate the computer that is running the Proxy Module, right-click on it, and choose Properties.
Check Trust computer for delegation. A message box warning you that "this is a security-sensitive operation and it should not be done indiscriminately" will pop up. Click OK.
Click OK to close the machine's properties, and close the Active Directory Users and Computers window.