I have a situation, where my server can't connect to an SMTP server, while my PC can. But the same server can connect to another SMTP server. I think that my firewall might be blocking it. How can I reliably test, if this issue caused by my firewall/iptables? Ideally, with or each one alone.
There are many rules in the iptables and I may miss things. I was thinking of a tool, which would tell me if a e.g. outgoing connection to a host at port with TCP or UDP would be blocked or not.
PS: it is a Debian server and my laptop and the server are in different networks.
