No Route to Host? Host is reachable from Scalix Server

[burhankhalid]

Hello:

Scalix has been running for quite a long time now, with no noticable issues. Except that for one particular domain (which resolves correctly) I always get the following in the maillog:

stat=Deferred: foo.zoo.bar.com.: No route to host

Which is strange since I can send ping/traceroute to the host without any problems. How can I begin to troubleshoot this problem? The host resolves correctly and checking it from an external source -- emails are delivered fine. Except for this one host, all other mail delivery is working as expected.

Regards,
Burhan Khalid

[chris]

Hi Burhan,

what output does the command dig -t mx domain.com produce? Is that the same host that is unreachable?

Can you do a telnet foo.zoo.bar.com 25 to send mail by hand to that server?

Cheers,

Chris

[burhankhalid]

Chris:

Thanks for your response, to answer your question:

The domain has three MX records. Mostly, the host that is tried is the first entry that comes up, but in testing Scalix has also tried to send to the next MX entry and that also comes up with no route to host. I have tried to telnet to all three MX hosts for the domain, and all come up with 'no route to host'.

I am thinking this is a problem with our ISP and their route and not with Scalix itself, but since being new I wanted to make sure that I hadn't overlooked anything.

Thanks for your time,
Burhan

Edit:

Earlier, the host was pingable by which I assumed it was online; hence the topic 'host is reachable'. Since the host is managed by the US Military, it could be that the host was online and the email service was down, but I doubt that. I think this is more and more a ISP problem and during our scheduled downtime I will follow up with them.

[chris]

Hi Burhan,

smtp is sent over tcp, ping is icmp, so it could also be firewall rules somewhere in between. If the host is pingable is will also in fact be truly routable. However, it might be a forwarded port or whatever. You'll want to follow up with the server's admin - check admin-c or tech-c on whois.

Cheers,

Chris