Jerry:

To answer your questions Adagio doesn't have the capability to fax from a central fax server. We have always had success with Multi-tech modems. For each workstation you will want a model MT9234ZBA external modem (we still use one to receive faxes). It's been so long I forget I forget how much time we spent on the learning curve, I can tell you that its been so long since we last set up a client to fax from Adagio that I've forgotten much about the setup and troubleshooting issues. If, as Andrew say, only a serial port will work then I'm not even sure if this is still an available option.

Don't attempt to use an internal model, in particular any OEM modem. As Andrew pointed out you will burn through a considerable amount of time trying to get it working reliably (and most likely fail).

Given that faxing is a dead technology, why is your client still faxing invoices rather than emailing them (which can also be done from Adagio)?