Scem (socio events manager) is an app for managing events. It's auto-managed by organizations. Social network aspect dominant. Example here: http://www.lebounce.com . If anybody interested by this app, contact us.
solution : make sendmail to not manage the domain. The domain must not be considerered as a local domain !
I deleted the entry into /etc/hosts for that
when we receive an email like a new pics was published ... the sender of this mail is not lebounce.com but do-not-answer@li148-6.members.linode.com