The location of the file is different for e-smith. After some frantic hunting around on some web sites that gave me a headache reading them, I found the file that you have to alter is /etc/rc.d/init.d/masq
However after copying the ip_masq_mms.o file to the IPV4 directory and making these changes, I've found that a recipient for a file transfer can see that I'm sending the file (an improvement over before) but no actual connection is made. Perhaps it requires a new ip_masq_mms.o file since MS made changes to Windows Messenger recently.
If anyone can help here I'd be extremely grateful.