Transport providers operate largely at the direction of the MAPI spooler. This places remote transport providers under some obligations in order to interact with other MAPI service providers. Remote transport providers should strive to operate in the background in order not to cause client applications to appear inactive. Remote transport providers should also strive to minimize their use of scarce resources, such as modems and COM ports, in order to permit other MAPI service providers and other user applications to use those resources if necessary.