ports and firewalls

setting up a mailserver to listen on ports 25 and 26

[dhardisty]

Hi everyone,

I've set up a custom mail server to listen for SMTP on ports 25 and 26. I am able to telnet from my home computer and get the server response on port 25, but not port 26. When I try connecting to port 26 from the server itself (using putty to connect to ssh), I am able to telnet both ports 25 and 26. This makes me think some kind of firewall is running and blocking port 26.

Any ideas on how to troubleshoot this? I don't know where to start. The server is a VPS hosting plan -- where I have root access to my partition. I've looked at the hosting documentation, but have not found any mention of firewalls. Please help. Thanks!

best,
Dave

[trillianjedi]

The server is a VPS hosting plan

You may need to email your host to find out if they're running a firewall on the whole box. Are you sure there isn't a local one running?

Certainly sounds to me like a firewall.

TJ

[dhardisty]

Thanks for your reply. I've contacted the hosting company. Is iptables a firewall? When I type "service iptables status" it says "Firewall stopped". When I try to start it, it has an error "lsmod: command not found" and is not able to start.

[mcavic]

Iptables is a firewall. But most VPS's don't support running a firewall on the virtual hosts.

Try: iptables-restore < /dev/null

That will delete all the firewall rules from memory. Then if you telnet from home and get no connection, it's a firewall on your physical machine or on your host's network. (It could also be your ISP blocking the port outbound, but I don't know why they would).

[dhardisty]

The iptables-restore trick didn't work, but I heard back from the host: "At this point we are blocking non-esential ports at the router level. We have put in a request to open up port 26 and that should be completed tonight (after 10pm EST)." -- hopefully that will take care of the problem.

Thanks for the helpful tips, guys. Sorry I'm such a newbie at Linux admin stuff.