A transport service library must register itself in the registry under the HKLM\PMail\ServicLibs key so that a client application can locate and load the DLL. Register Smtp.dll as the SMTP subkey.
All interactive transport services must register with the client application so that a user can choose one for connecting to the server. An interactive transport is the transport that appears in the service list visible to users. On the other hand, passive services are those that deliver mail without requiring the user's interaction. In Inbox, interactive services are added to the Service menu once they are registered as a named key under HKLM\PMail\ServiceInfo. If the user removes an interactive service, Inbox deletes the associated registry entry. Passive services are registered as a named key under HKLM\PMail\PassiveServiceInfo. The client uses the passive service registration information to allow the user to select the transport for outgoing messages. Unlike interactive services, passive services have no subkeys.
The user can add registered interactive services to the Service menu of the Inbox application by tapping the Compose menu followed by the Options dialog box, and then the Add dialog box. The following sections provide sample registry entries and demonstrate how to install a transport service and add it to the Inbox client application.