1. A computer-implemented method comprising: receiving original content associated with a first language from a first client machine; translating, using one or more processors of a computing system, the original content to machine-translated content associated with a second language; determining individual confidence scores for a plurality of expressions of the machine-translated content, each expression comprising at least one of a word or a phrase; determining individual probability scores for the plurality of expressions; determining individual combined scores for the plurality of expressions from the individual confidence scores and the individual probability scores; determining, based on the individual combined scores for the plurality of expressions, that a part of the machine-translated content fails to satisfy a quality threshold; transmitting a part of the original content corresponding to—the part of the machine-translated content failing to satisfy the quality threshold to a second client machine; and receiving a translation of at least the part of the original content from the second client machine.