Just got off the phone with Multi-Tech Systems technical support regarding their fax modems with serial interfaces. I use several MT5634ZBA class modems with various clients.
You can use a Serial (DB9 M) to USB adapter with their Fax Modems should you wish to do that either to your new hardware SBS Server 2008 (or any other hardware – of course). They did not have any specific recommendation as to any particular brand/model and they don’t sell them. After asking if they had any specialized pin out, they do not; it is straight through.
To get the serial adapter cable to work requires the proper driver. Until just recently there wasn’t a suitable x64 bit driver. But I have found one, downloaded and installed it, and have my Multi-Tech modem now functioning with the SBS 2008 x64 Premium Server. There is a ‘chip’ in the adapter and that manufacturer is Prolific. http://www.prolific.com.tw/eng/downloads.asp?ID=31
Also, you can now buy fax modems with USB interfaces.
FYI – They were very nice to speak to and fast in getting to the point of answering my question – no phone system labyrinth, no challenging dialect, professional, competent. It was refreshing.
Also, there isn’t any value in worrying about V.92 speeds with data faxes as the receiving fax devices are likely no faster than 33.6K and so this slow speed is normal just be aware of any long distance charges and perhaps set up a 1-800 # if volume warrants this.