Resolved ipset causes problems with webmail

[roadrash]

Hello,
I installed IPtables on Plesk Obsidian. dnf install iptables iptables-services
No problems so far.
Also Plesk Fail2ban is working like a charm.

I use a very good set of firewall rules for many years now and wish to continue that.
Also like to use ipset too, then get nightly updated rules with IP's from several blacklists. Very satisfying and very effective.

However. Now i installed this on a Plesk Obsidian machine (AlmaLinux8) but webmail (both Horde and Roundcube) are throwing Internel Server Error.
This starts right after: dnf install ipset

When removing ipset, then al works again like before.
Did the same on a testing box. Same problem.
Is something mixing up?
Does anyone have a clue?

Thanks

 

[roadrash]

Found the problem and fixed it.
ipv6 was bogging me.
Apparently Dovecot uses it and i accidentally blocked of some ports.