Fax on Small Business server 2003

I’ve installed a fax machine on our server downstairs, an old external 56k v90 modem. From the advice of some posts I’d read here and elsewhere, i chose the generic windows drivers.

It seems to work perfectly for incomming faxes, routes them to the receptionists email perfectly

But when i try and send them I get the error “fatal error” in the extended status part of the server fax console.

Does anyone have any suggestions?