Are you using Microsoft Windows? “Microsoft Fax” is the fax software included in business editions of Windows. Do you have a VoIP System? SIP T.38 compatible VoIP gateway, IP-PBX or VoIP service provider. Install the VoIP Fax Plug-in and try it! This plug-in enables Microsoft Fax and Windows Fax & Scan, which are built right into Windows, to send and receive faxes using your VoIP infrastructure without any further cost. Offering you a simple desktop fax solution, with easy print-to-fax capabilities.