While this has nothing whatsoever to do with Word or mail merge the answer
is that you don't. You need a fax capable modem connected to a telephone
line and fax software capable of driving it. Windows XP and some of the
business oriented versions of Vista include such fax software.
--
Graham Mayor - Word MVP
My web site
www.gmayor.com
Word MVP web site
http://word.mvps.org