Linux

Your best change to get ahead in this problem is by visiting a site called www.hylafax.com. Its the far best free (gpl i im not mistaken) faxserver available and it also, you can use it to fax from windows machines. There's good documentation on hylafax site which modems work and which dont and how to setup things. Also they provide extensive linkdirectory to all available 3rd party clients that can use hylafax services from network.

Other that Hylafax. Is there any other software also. This i am trying to test.