I have a client that is using this device to fax documents. For some reason, they are unable to fax to several companies. It is a very consistent problem. There are several numbers that they can fax to without a problem. However there are also 3 numbers where they can't fax to. The fax machines connect and talk to one another - however halfway through their handshake, the modem noise just hangs and eventually the connection drops. We've already confirmed that these businesses are having no problems on their end. They are able to receive faxes from other sources. As I said, it is a very consistent problem. The client faxes a document to someone every morning and the faxes always goes through to the recipient. However, the client has never been able to send a fax to these 3 numbers. We've already tried a myriad of things already. We've replaced the cord from the fax to the wall, updated the firmware on the device, contacted HP (they were of little help). I was thinking about disabling error correction? Any help would be greatly appreciated!