From: Ben Reisner (benimperialwebdesigns.com)
Date: Wed Dec 19 2007 - 10:53:33 CST

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I operate a number of mail servers behind a firewall. My postfix box is
currently having trouble delivery mail to some domains that I recently moved
to a different box. The issue is that when postfix uses DNS to resolve the
IP address of the host indicated by the MX record. DNS gives back the
public IP address, which does not work because my firewall+router block that
kind of going out and going back in type of scenario. It gets a 'connection
timed out' message.

When I had this type of situation on my windoze boxes I used an etc/hosts
file to specify the private ip of all relevant mailservers. I made such an
entry on my postfix server. I can now telnet into port 25 with the
appropriate name, however when postfix tries to send a mail out, it still
gets 'connection timed out', and I still see it attempting to use the public
ip (ignoring the hosts file)

I found a post on the net referring to 'smtp_host_lookup = native,dns' and I
put that in and tried to reload and stop/start postfix, but it still doesn't
seem to have an effect.

Any ideas what I could be doing wrong?

#postconf|grep version

mail_version = 2.2.10

# postconf|grep smtp_host

smtp_host_lookup = native,dns

Dec 19 11:03:15 yin2 postfix/smtp[7148]: 5CC7DEA147F:
to=<testemailproblemdomain.com>, relay=none, delay=1636, status=deferred
(connect to barracuda.imperialcable.com[64.115.170.228]: Connection timed
out)

# cat /etc/hosts

127.0.0.1 yin2.imperialcable.com yin2 localhost.localdomain
localhost

192.168.10.11 mail.imperialcable.com mail localhost.localdomain
localhost

192.168.10.45 barracuda.imperialcable.com barracuda

Ben Reisner

Imperial Web Designs

516-797-7302

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