The key consideration is that unless the information that Asterisk knows about the fax is sufficiently detailed, it may not be possible to deduce the intended recipient without having someone actually read the fax (it is common for a fax to have a cover page with the recipient's information written on it, which even the most capable text recognition software would have a difficult time making sense of).
In other words, unless you dedicate a DID to each user who might receive a fax, Asterisk isn't going to be able to do much more than send all faxes to a single email address. You could code something in the dialplan to handle this, though, or have an external cron job or other daemon handle distributing the received faxes.
You may have a dedicated phone number for receiving faxes. However, with Asterisk, that is not a requirement. Asterisk has the ability to detect that an incoming call is a fax and can handle it differently in the dialplan.
* Asterisk is registered trademark of Digium.
@ 2017 © KingAsterisk Technologies. All Rights Reserved