Disable your Firewall

Linux has an plethora of annoying firewalls, in general, the thing to do is to turn them off as they don’t do anything useful :-), it’s also a good way to figure out that the firewall is the problem. Then later if you want a firewall for some reason, you can enable one. Sadly there is no way to know which firewall you have.

nft flush ruleset
systemctl mask nftables.service

systemctl stop firewalld
systemctl disable firewalld

service iptables stop
service iptables disable

service ipchains disable
service ipchains stop

iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X

cfx -x

reboot - then test if you have succeeded with telnet

telnet netwinsite.com 25