Recently our server (firewall+web+mail+pppd/pppoe ADSL)
developed a very strange problem.
(I think it happened after a power outage):
It can no longer connect to anywhere on port 25 that lies beyond its ADSL link.
No matter which mail server I try to connect to, it pauses for 15 seconds and gives a:
"No Route to Host." here is an example:

# telnet 122.222.111.222 25
Trying 122.222.111.222...
telnet: connect to address 122.222.111.222: No route to host
telnet: Unable to connect to remote host: No route to host

(I made up the 122.222.111.222 address)

However, if I chose any other (valid) port at the same address, such as 80 or 110, it works; it connects fine. Only port 25 is giving me headaches.

This is really baffling, and I don't understand what happened. We did not change the firewall rules or pppd settings.
Its netstat -rn looks good, no oddity with its routing.

Any ideas what I should check?
Thanks!
-t

I think it is a firewall problem. May be a wrong rule ?
Try to disable the firewall and try the connect test again. Re-enable the firewall as soon you finish the test.

If it is a firewall problem, print the firewall rules, "iptables -L" an dpost it here to help us to debug it.

Hi There,

Having worked at a major hosting company for a few years now, I can say confidently that this is likely an ISP problem. ISPs tend to ban outbound port 25. That is why if you have another box on your LAN you can connect fine. However, if you try to connect to something out in the tubes, no dice. This is a preventative measure against spam set forth by most ADSL / Cable ISPs I know of.

Try calling your ISP to see if they can add an exception, or if their business package allows for this. I don't suggest sending out email from an ADSL source anyway. That is a good way to get your mail flagged for spam (Many people auto-flag mail that originates from a dynamic subnet (ex. Cable / DSL ISPs).

You can always try Tunneling or setting up a mail gateway that listens on an alternate port. Most mail server software provides a functionality to set alternate ports.

------------------------------------
Michael Piekarski
Network Engineer
mpiekarski@hostmysite.com
www.hostmysite.com

what happens when you run a traceroute?