In this paper, we propose an ontology-based approach that enables to detect the emergence of relational conflicts between persons that cooperate on computer supported projects. In order to detect these conflicts, we analyze, using this ontology, the e-mails exchanged between these people. Our method aims to inform project team leaders of such situation hence to help them in preventing serious disagreement between involved employees. The approach we present builds a domain ontology of relational conflicts in two phases. First we conceptualize the domain by hand, then we enrich the ontology by using the trigger model that enables to find out terms in corpora which correspond to different conflicts.