The problem was due to a change of platform at ouvaton.coop (our domain host)
For some days there were two IN A records for csjl.fr : our IP (193.251.185.154) and Ouvaton's IP (213.152.29.60) that had been added automatically during the change of platform.
The extra IN A record has been deleted and it works again.
Thank you all for your tests and advice which helped to understand the problem.
Best regards
i put resolved in the title