Then go to the fwdfile-directory and edit the config.mk file.
   ($ cd mail_fwd/fwdfile; vi config.mk)

   Here is a list of the options availible in config.mk

   BINDIR : This is the directory where to put the compiled and installed
         wfwd file. If this parameter is changed you must also change
         the $mail_fwd_wfwd_binary path in setup.php.
         Default is /usr/local/sbin/

   WEBUSER : Should be set to what ever user your webserver is running as when
         parsing the squirrelmail php scripts.
         Default is www-data

   XTRA_CC_FLAGS : Extra flags passed to the C compiler.
         Mac OS X users must add the flag -traditional-cpp


4) As root compile and install the wfwd binary.
   $ make
   And if no errors occur
   $ make install