Ok, I thought froxlor has been responsible for the /etc/iptables/rules.v4, sorry.
That froxlor was not, is a very important info for me, thank you very much!
I have to find out now, where those existing iptables came from. My only candidates at the moment are
* the existing rules are a default in the OS Linux image of my Hoster?
* the existing rules were generated during a Wordpress Installation?
Anyway, it is good to know, that froxlor cannot overwrite those persistent rules.
Kind regards