Exchange 5.5/SP1 can add originator domains and user names to a Turf table, so that messages arriving from these entities can be deleted, or saved in a Turf folder. The default is C:\Turfdir. These messages are NOT delivered to the receipient.
You can alter the Turf folder location by using Regedt32 to navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\Services\MSExchangeIMC\Parameters\Turfdir
and altering the location.
NOTE: Every time you use the Exchange Server Administrator
Configuration / Connections / Internet Mail Service / Connections / Message Filter
to add an object to the Turf table, the Turf folder is reset to the default location. If this folder does not exist,
the messages will be lost.