This article reports an experiment with the circulation of an email message among former students of an engineering school. Based on a particular research protocol (enrolment of a graduate, use of a relevant motive, participant observation in the circulation of the email, collection of addresses, research on the identities of the participants), the author observed the modes of circulation of an email message and reconstructed the 'chains'? of participants. She thus identified three distinct forms: first, the most common (7 out of 10 cases), consisting of a short chain comprising pairs of graduates who had become friends; second, broad and short chains, consisting of graduates employed in a particular industry (aeronautics and defense) and resembling a small world; and, finally, a single long chain in which professional contacts seem to prevail over sociability between friends, at least e-sociability. The article ends with the question of the nature of 'Internet'? interaction between alumni.