Server debian 8 with seafile 6.1.1, mail sent received as unknown

I have installed seafile on server without any problem.
Just now I remark even after have tried to change parameters in, mail are sent, unfortunately after have inform sender field or made REPLACE_FROM_EMAIL = True. All mail sent are received at mail box recipient as unknown (“inconnu” in french) so classified in spam box.
Do you think it could be a problem with debian version or seafile version ? all other seafile functions works good.
Thanks in advance.