This study used sequential exploratory, mixed-method research that explored the influence of authentic tasks on adult language learners' interactions in e-forums. The participants belonged to a blended-flipped program of English as a Foreign Language (EFL). E-Forum posting in the course aimed at encouraging beginner learners to exchange experiences; however, participation in the e-forums did not evolve into spontaneous interactions. Therefore, authentic tasks were designed and implemented in the e-forum. Data were gathered from learners' participation registers, surveys, and interviews and by executing a content-analysis procedure. After analyzing the data, one main category and three subcategories emerged. The main category showed that implementing authentic tasks on students' e-forums interactions led to the collaborative construction of a cognitive-social e-learning environment. The main category comprised three subcategories: (a) building a learning community by interweaving affective-communicative actions, (b) promoting an online learning environment through authenticity, and (c) moving from individual to collective knowledge construction. Findings suggest that the implementation of authentic tasks on e-forums: (a) increased learners' meaningful interactions mediated by social, cognitive, and teaching presences; (b) helped to construct significant and lifelong knowledge collectively; and (c) fostered a stronger learning community through participants' affective-communicative actions.