DNS tells mail to go to the wrong host? (Sorry, long post here..)

David Cunningham newsonly at please.com
Wed Oct 6 06:12:05 UTC 1999


I have 3 computers on a private network.  I'm attempting to learn the DNS
issues of mail routing.  All hosts in this discussion are all on my private
network.

I can't send any email from mercury.alpha.com to neon.beta.com.  I'll cover
the problem in a second, but first you need to know a little about my
network.

CONFIGURATION:

There are 3 computers involved, all on the same subnet (10.10.10)  My
Windows machine is poweron.alpha.com (10.10.10.10), the Linux box is
mercury.alpha.com (10.10.10.20) and the other Linux box (argon) is set up
with 2 IP addresses and domain names.  Argon is configured as
argon.alpha.com (10.10.10.30) and neon.beta.com (10.10.10.40).  I'm doing
this to simulate a virtual hosting business.

My intention is to use argon to receive mail for several different domain
names.  This is why both IP addresses ...30 and ...40 are both on this
machine.  The name server is on mercury.

I have included my DNS db files at the end of this posting so that you can
figure out my mistakes 8-).

PROBLEM:

Here's the deal.  I want to be able to send mail from my windows machine
through sendmail on mercury to neon.beta.com.  So far I can't do this.  When
I try, I get a sendmail delivery error from mercury saying the user does not
exist.  Of course I have verified that the user (david at beta.com) does in
fact exist.  In fact I tried to send mail directly to david at beta.com by
setting up Outlook Express (on Poweron) to use neon.beta.com as the SMTP
server and it gets through fine.  So here is the conclusion I'm drawing.
Neon can receive mail for beta.com fine but mercury is not routing the mail
to it.

To confirm this I unplugged neon (aka argon) from my hub and tried to send
mail to david at beta.com by way of mercury again.  Again Mercury says the user
is unknown.  This is weird considering sendmail on mercury can't even talk
to sendmail on neon.  This has me thinking that maybe for some reason
mercury is trying to deliver david at beta.com to it's own local mailboxes.

So I created a david account on mercury.  Now mercury happily delivers
emails for david at beta.com to it's own david account.  This is not the
desired result.  Beta.com should be on neon, not mercury.

So here's the challenge.  How do I get mercury to deliver mails for
david at beta.com to neon?  Again beta.com is indeed specified as being on neon
in the DNS db files (see below).  What am I doing wrong?


NAMED.CONF

options {
 directory "/var/named";
 /*
  * If there is a firewall between you and nameservers you want
  * to talk to, you might need to uncomment the query-source
  * directive below.  Previous versions of BIND always asked
  * questions using port 53, but BIND 8.1 uses an unprivileged
  * port by default.
  */
 // query-source address * port 53;
};

zone "." {
 type hint;
 file "named.ca";
};

zone "0.0.127.in-addr.arpa" {
 type master;
 file "db.127.0.0";
};

zone "alpha.com" {
 type master;
 file "db.alpha";
};

zone "10.in-addr.arpa" {
 type master;
 file "db.10";
};

zone "beta.com" {
 type master;
 file "db.beta";
};


DB.ALPHA

@       IN      SOA     mercury admin  (
                                      1          ; Serial
                                      28800      ; Refresh
                                      14400      ; Retry
                                      3600000    ; Expire
                                      86400 )    ; Minimum

;Nameservers
  IN NS mercury

;Mail
  IN MX 0 mercury

;Hosts
poweron  IN A 10.10.10.10
mercury  IN A 10.10.10.20
argon  IN A 10.10.10.30


DB.10

@       IN      SOA     mercury.alpha.com. admin.alpha.com.  (
                                      1          ; Serial
                                      28800      ; Refresh
                                      14400      ; Retry
                                      3600000    ; Expire
                                      86400 )    ; Minimum

;Nameservers
  IN NS mercury.alpha.com.

;Hosts
10.10.10 IN PTR poweron.alpha.com.
20.10.10 IN PTR mercury.alpha.com.
30.10.10 IN PTR argon.alpha.com.
40.10.10 IN PTR neon.beta.com.


DB.BETA

@       IN      SOA     neon admin  (
                                      1          ; Serial
                                      28800      ; Refresh
                                      14400      ; Retry
                                      3600000    ; Expire
                                      86400 )    ; Minimum

;Nameservers
  IN NS neon

;Mail
  IN MX 0 neon

;Hosts
neon  IN A 10.10.10.40



If you would like to know anything else to help solve this please ask.
Thank you for any feedback.





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