Computer-supported collaborative learning (CSCL) has been the subject of a wide range of studies over the last twenty years. Previous research suggests that CSCL exchanges can facilitate group-based learning and knowledge construction among learners who are in different geographical locations [Littleton, K. & Whitelock, D. (2004). "Guiding the creation of knowledge and understanding in a virtual learning environment." "Cyberpsychology & Behaviour," 7(2), 173]. A less known fact, however, is that successful CSCL exchanges depend on the social interaction that takes place among participants. This social interaction is crucial, since it affects both cognitive and socio-emotional processes that take place during learning [Kreijns, K., Kirschner, P., Jochems, W. & Van Buuren, H. (2004). "Determining sociability, social space, and social presence in (a) synchronous collaborative groups." "Cyberpsychology & Behaviour," 7 (2), 156]. Nevertheless, its presence in these exchanges should not be taken for granted, since there are certain barriers which may impede interaction; for example, students may not know each other previously (high social distance) and requests and offers which appear recurrently in collaborative learning messages can threaten the participants' negative face (Brown and Levinson 1978, 1987). In order to explore how participants overcome these barriers, we have analysed the linguistic features of politeness strategies used in the introductory e-mails exchanged between eleven students and their partners, who are students of English and Spanish, respectively. Our findings show that partners in collaborative e-mail exchanges do not use negative politeness strategies as often as we might expect in encounters where the social distance between participants is high, but they rely heavily on positive politeness strategies, especially those relating to "claiming common ground", "assuming or asserting reciprocity" and "conveying cooperation". The presence of these strategies would indicate that fostering closeness, solidarity and cohesion becomes the priority to be achieved between the partners, instead of the expected negative politeness mechanisms whose aim is to demonstrate high social distance and, therefore, formality and impersonality.