Le serveur IMAP n'est pas joignable

Hi,
I have installed nextcloud with helm charts on windows10:
helm install nextcloud nextcloud/nextcloud --namespace nextcloud
and I have the mail app enabled.

Now I want to configure my e-mail account with the following params:

IMAP Server: imap.nordnet.fr
Port: 143 (STARTTLS)
User: xxx.yyy
Password:

STMP server: smtp-auth.nordnet.fr
Port: 587 (STARTTLS)
User: xxx.yyy@nordnet.fr
Password:

but I always get the erreur message: Le serveur IMAP n’est pas joignable.

What did I miss ?

Many thanks in advance !!!

A lot of things can cause trouble setting up access to an external email server, like e.g. certificate issues etc. Here you find further information about how to set-up the Mail app and also information on how to enable e.g. the debug mode: