can't send emails from code via pro2.mail.ovh.net

hi

we've sent hundreds of e-mails from our app (via pro2.mail.ovh.net), and suddenly, from thursday (02/13), we've been unable to.

sorry the error message is in french :

System.Net.Mail.SmtpException: Échec d'envoi du courrier. ---> System.IO.IOException: Échec de l'authentification, car le site distant a fermé le flux de transport.

(roughly : failure to send - authentication error, remote site has closed transportation flow)

does anyone have any idea on this ?

thank you all