The default SMTPD banner in Postfix is $hostname ESMTP $mail_name, which normally translates to something like <your_host_name> ESMTP Postfix.
If the internal server name does not match the public DNS, the SMTP shows a hostname which may be incorrect, and make some email services reject messages or mark them as SPAM.
It would be useful to have a way to override the default Postfix smtpd_banner configuration option.
This can be done as easy as including a new template snippet named /etc/e-smith/templates-custom/etc/postfix/main.cf/40smtpd_banner_host wit the following content:
I pasted your cmd line on my server and it worked flawlessly.
It seems you have some problem with your installation, you don’t seem to have the directory /etc/e-smith/events/nethserver-mail-server-update (and you should!)
This directory is the configuration dir for the event you need to fire. Perhaps you can restore this directory from backup?