A network scanner, communication protocols, and client and server programs and are provided which provide an improved way to transmit legally binding documents, obviating the need for outmoded, legacy fax transmissions. Using the network scanner, a document may be scanned and transferred directly into any shared folder inbox residing on any computer attached to the Internet. Enhanced server systems and network communications and messaging protocols are provided that are more practical to use than email for sending documents such as executed legal documents or other documents requiring robust integrity and authenticatability. Similarly, the inventive network scanner, server systems and communication protocols provide improved ways to perform large file transfers and to manage bandwidth to minimize problems associated with uploading/downloading large files as attachments to/from email servers and for enabling user control over VoIP quality during file transmission sessions.