we use it to send & receive faxes because we don't want to buy a fax machine :-)

I have a small 50 line ruby script that converts attachments from emails into outgoing faxes, and a 10 line ruby script that converts incoming faxes into emails with a pdf attachment.

You should try freeswitch instead -- the rxfax thing from Asterisk would sometimes truncate incoming faxes. Not sure why.