A system comprises an input interface to receive input indicating a question, a communication module to establish a communication link with an access network, wherein the communication link provides connectivity to one or more packet data networks (PDNs) via the access network, and a computer coupled to the input interface and the communication module, the computer including a processor and a memory, the memory storing instructions executable by the processor to execute an information retrieval procedure including accessing an open-domain context search space of the one or more PDNs and retrieving, from among a plurality of contexts of the open-domain context search space, a plurality of candidate contexts for answering the question using a question-answering model for open-domain question answering, identify a set of non-answering contexts among the plurality of candidate contexts, wherein each of the set of non-answering contexts is a respective context for which the question-answering model predicts the question to be unanswerable, determine an open-domain unanswerability score for the question based on respective relevance scores for the set of non-answering contexts, determine an open-domain result for the question based on the open-domain unanswerability score for the question, and output result information indicating the open-domain result for the question.