Backboning is the process in which two similar systems are connected by a dissimilar one. Backboning is more than simply enabling messages to flow between two sites that are not directly connected. The process can allow otherwise unconnected Microsoft Exchange Server sites to behave as part of the same organization. For example, two geographically separated Microsoft Exchange Server systems can set up a backbone over a foreign system. The two sites can then be part of the same Microsoft Exchange Server organization, even though the two sites exist on separate LANs.
Backboning over the Internet
The backboning process imposes special requirements on a gateway. The gateway must provide seamless addressing and communication throughout the entire backboning process, even when the message format of the foreign system cannot support some features used by Microsoft Exchange Server. In the scenario illustrated above, the messages might have features, such as rich text formatting, that the foreign system cannot handle. The MAPI SDK and the Microsoft Exchange Server SDK provide functions that enable gateways to encode such features so that they may pass safely through the foreign system.