In addition to the standard provider and logon objects implemented by all service providers, transport providers are required to implement a status object. For the other service provider types, implementing a status object is optional. However, MAPI requires it for transport providers. Transport providers that support the downloading of message headers from a remote server also implement a folder and a table.
The following illustration shows each of the objects that transport providers can implement with their corresponding interfaces and indicates whether MAPI or a client is the object's user.