VAN or Value Added Network is a mailboxing system that acts as an intermediary. Each trading partner periodically connects to their mailbox at the VAN, sends any EDI messages for other trading partners on that VAN, and picks up any messages left for them. Although there are a number of separate VANs, they can pass files to each other to a greater or lesser degree. Communications to a VAN mailbox can typically be very simple using dial-up modems.