Thank you, sir.
You are right in that ChatGPT is stupid. But, you know, when one is frustrated by days of struggle, any word of sympathy seems useful...
The fail2ban itself works - rules are OK and find all correctly.
But for some reason fail2ban creates hundreds of chains with the same name f2b-recidive which remains empty.
Looking into daemon.log just now I see errors like:
2025-01-10 20:23:09,306 7F557DFFB700 ERROR 7f55a4081450 -- exec: iptables -w -F f2b-sqpsmtpd; iptables -w -X f2b-sqpsmtpd 2>/dev/null; iptables -w -N f2b-sqpsmtpd; iptables -w -A f2b-sqpsmtpd -j RETURN; iptables -w -I INPUT -p tcp -m multiport --dports "25" protocol=tcp -j f2b-sqpsmtpd
2025-01-10 20:23:10,776 7F557DFFB700 ERROR 7f55a4081450 -- stderr: "Bad argument `protocol=tcp'"
or
2025-01-10 20:23:09,313 7F557DFFB700 ERROR Failed to execute ban jail 'sqpsmtpd' action 'iptables' info 'ActionInfo({'ip': '87.120.93.10', 'fid': <function <lambda> at 0x7f55a4ab38c0>, 'family': 'inet4', 'raw-ticket': <function <lambda> at 0x7f55a4ab3e60>})': Error starting action Jail('sqpsmtpd')/iptables: 'Script error'
I tried many variants, but...
As all these errors seems to be originated from errors in jail.conf and/or iptables-multiport.conf, I thought that looking at a working setup I will be able to find correct definitions.
I understand also, that most probably my errors are not emposed by SME10 configuration/operation.
This was also the reason of my kind request to receive the working setup.
Thanks a lot.and excuse me.