Issue Send and receive email don't work

[beuzathor]

Hello,
I created several accounts and tried to configure them under thunderbird but none worked. The server is closed.
I also tried going directly through roundcube but the still neither sends nor mail reception works.
When I try to send an email via roundcube I systematically the following error : Erreur SMTP (-1) : échec lors de la connexion au serveur.

I have do nothing special on this server (no customisation). Mail service are online so i don't understand.
I tried on many domain for to be sur it's not a DNS problem.

Someone have an idea for a solution ?
Thanks