How should we go about receiving faxes with a server?

How should we go about receiving faxes with a server?

What kind of software is there for receiving faxes from a computer? I want to be able to run it on a server so it's always receiving. Something that flexible with how it stores the faxes, and how it sends notifications would be good. I'd also like a good API or some way of adding custom functionality to it for notifications and such.