Machine-readable codes are read, decoded and resolved by a messaging system in order to perform a desired function. If the code is not native to that (home) messaging system, then a resolution request is made to a central messaging interchange system to determine which other (destination) messaging system is native to and can resolve that code. The messaging interchange system then either returns the appropriate routing information back to the home messaging system (in which case the home messaging system sends the resolution request directly to the destination messaging system) or forwards the resolution request to the destination messaging system itself. The destination messaging system transmits a resolution response message to the home messaging system, either directly or via the messaging interchange system.