When Plesk Firewall extension is used, the following rule is added at the beginning of the list(at
CONFIG_TEXT: apply_rule /usr/sbin/iptables -P OUTPUT DROP
What's its purpose?
It is pre-pended by default in order for the specific rules to be applied before allowing access to the server to make sure it is not accessed by the clients from the blocked subnets.
Once the other rules in the from the extension's list are applied, the following one overrides the earlier DROP rule:
CONFIG_TEXT: apply_rule /usr/sbin/iptables -A OUTPUT -j ACCEPT