We consider communication between a source and a destination in the presence of one or more relays and an external interferer. The external interferer communicates with its own destination; however unlike the interference channel, the interferer has a fixed codebook and is not willing to update its strategy to aid the source-destination communication. We consider various scenarios in which the interfering signal is known either at the source or the relay(s). For each scenario, assuming Gaussian channels, we study network configurations under which exploiting the interference structure, rather than treating it as an unstructured state sequence, is beneficial in terms of communication rates.