Based on recent studies, computer-mediated communication (CMC) has been considered a tool to aid in language learning on account of its distinctive interactional features. However, most studies have referred to "synchronous" CMC and neglected to investigate how "asynchronous" CMC contributes to language learning. Asynchronous CMC possesses features distinguishable from synchronous CMC (e.g., more accurate, complex, formal, and longer utterances than those in synchronous interactions). The discourse structure in such interactions should be different from that in synchronous interactions, and it is necessary to investigate how such features can facilitate second language acquisition. This study investigates task-based email interactions among 24 native speaker-non native speaker (NS-NNS) dyads with respect to the negotiation structure and strategies followed in asynchronous CMC. The findings underscore the potential of syntactic development, the necessity of instruction in effective feedback strategies, and the distinguishable negotiation structure of asynchronous CMC. (Contains 9 tables, 1 figure and 1 note.)