All the examples related to faxing use the Unix/Linux path, such as originate sofia/external/100@10.10.10.10 &txfax(/path_to_fax_file) <extension name="fax_transmit"> <condition field="destination_number" expression="^9979$"> <action application="txfax" data="/tmp/txfax.tiff"/> <action application="hangup"/> </condition> </extension> I have tried "C:/tmp/fax/txfax.tiff" or "C:\MyJob\fax\txfax.tiff" or "C:\\MyJob\\fax\\txfax.tiff" without any luck. I got an error like [ERR] mod_fax.c:518 process_fax() Cannot send inexistant fax file, or the app crashed. Any help is greatly appreciated!