hi,
we're used to sending e-mails from our application, and we've sent many of them for years.
and since thursday (02/13) we receive an error message each time we try to send an e-mail from our app :
(sorry the original message is in french)
System.Net.Mail.SmtpException
'Failure sending mail.'
System.IO.IOException: Échec de l'authentification, car le site distant a fermé le flux de transport
(something like "Authentication error, remote site has closed the transport flow")
everything works fine from the webmail...
we're using pro2.mail.ovh.net as a server.
any ideas ?
thanks a lot
14978 
21.12.2025 10:15
Hello,
Is your application software written in French ? The error message is raised by the application, and not by the server.
E-mail sending must use port 587 and use STARTTLS encryption.
sorry I created 2 topics at the same time.
"Hello, please create a support ticket, as it seems to be an incident."
it seems like we dont' have necessary support level.
if it comes to this we'll upgrade our subscription.
but yeah, the port is in fact 587.
I can't find where to state the STARTTLS parameter though.
and it's written in french because of our OS I guess.
(oui j'avais créé le sujet sur le forum EN pour toucher plus de réponses, mais bon...)
we found the solution, it was the TLS version that was incorrect (maybe they deactivated 1.0 and 1.1).
thanks again.
Thanks for the feedback.
Interesting to know they have disabled the deprecated crypto. That may explain some other incidents.