just to confirm what you mean by this "Do a two-step process then - first receive the fax, then send it out again to a T.38 capable destination, using Free Fax for Asterisk."
a) are you referring to inbound faxing alone?
b) how do i ensure 100% reliable fax messages? say if my customers send my faxes, I need to make sure it will reach 100% of the time (assume there's concurrent channels for them to fax in - no busy tones, etc). R.711 u-law and a-law can cater this?
c) if i first receive the fax (users -> fax via pstn -> receive via my isdn), then send it out again to T.38? Hmm? mind to illustrate further on this? Do i need gateway or something to get this working?