A simple voice prompt or tone may help. If the sender enters the wrong extension, then the Fax Administrator will receive it and can route it to the right person. The first requires a computer system with a fax board. There is no keyboard, disk drive, or monitor. The unit plugs directly into the network.
Software is loaded from a user's workstation onto the file server.
The answer, technically, is yes, but at a price. The file server is already handling a multitude of tasks. By installing a fax board into the file server, the file server will have to do more work. It's not a clear-cut decision, since it depends upon how much work your file server handles now and how much faxing your firm expects to do. As a consultant, I tend to be conservative, since network performance and network downtime are a major issue.