So to clarify, you have no problem with email at this point, you are concerned about the results of a random/unspecified ssl checker? Most likely you just want to ignore the ssl checker, unless you have done something to configure your system in a particularly insecure manner. What details/basis for their claim of being insecure do they give you? Your connection used tls 1.3 with a good cipher; I don't know enough about cryptogaphy/key exchange to comment beyond that:
Note I just realized the '//email/test From:' is a link to checktls.com, and from their page I see that you are to email them when running their test, so ignore the above comment about an incoming smtp connect, it is unrelated to your test.
Is there a chance to get a isp3config installion plain config for postfix (main an master) and the config for dovecot (if needed) in order to setup from zero. Or ist there a command to recreate the configs for postfix and dovecot (if neded) ?
To recreate config run ispconfig_update.sh --force and let it reconfigure settings. This can be done by not using ISPConfig and just installing and configuring postfix and dovecot manually.
My guess is that he is asking for the default ispconfig configuration? If you are using a recent version of ispconfig, you can use Code: ispconfig_update.sh --force to re-run the update script. When asked to "Reconfigure Services?" select "yes" or "selected" and say yes for "Reconfigure Postfix and IMAP/POP3". This will rename your config files and install new ones.
