We report on evidence of pragmatic development in L2 email writing in a computerized diagnostic language assessment (C-DLA) administered to a group of Japanese English L2 learners (n=20). The pragmatic aspect of English L2 email writing is often a challenge for learners who are expected to appropriately vary their language choices according to contextual factors, such as their relationship with the receiver, and the purpose of the communication. Assessments consisted of the writing of four emails, based on given scenarios related to participants’ academic and daily lives. The C-DLA automatically identifies instances of pragmatic failure and provides individualized, immediate feedback to the learner. Following the graduated prompt approach to feedback, feedback increases in explicitness until an identified problem can be resolved by the learner. Task administration was carried out twice, with a two-week delay between the two. Evidence of pragmatic development was indicated by i) a decrease in identified instances of pragmatic failure both within and between administration sessions; and ii) a decrease in the level of feedback explicitness required to allow participants to successfully resolve pragmatics-related problems identified by the programme.