Sendmail/DNS interaction problem.

M.Ashcraft at epixtech.com M.Ashcraft at epixtech.com
Wed Aug 23 18:46:15 UTC 2000



The message means that the receiving mail server could not resolve your
name.  Reverse lookups are typically done to block SPAM with bogus from
addresses.  (So now they just fake someone else's domain to get around it.)
It would be helpful to know what mailer they are using as that may give a
clue to it's behavior.  Your MX records look good from here.  There is no A
record for blue-bell.com.au but that is typical.  If their mailer is
looking for this A record instead of the MX record it should be looking for
that could be the problem.

My best guess would be to add an A record for your domain name that points
to one of your mail servers.

You could also try to see if they will accept and can send mail from/to
luke at enterprise.blue-bell.com.au.  This would point to the above
resolution.  It looks like a problem with their mailer though.  Possible a
misconfigured or bad antispam filter.

Adding the A record would just be patching your system to deal with their
problem.  If you point it at 139.130.87.159 It would have the side effect
of making your web site available at http://blue-bell.com.au which may be
desirable.

The only other thing I see is that you are publishing your internal 192.168
addresses.  From Dig:
;; ANSWER SECTION:
www.bell-bird.com.au.   1D IN CNAME     enterprise.bell-bird.com.au.
enterprise.bell-bird.com.au.  1D IN A  139.130.87.159
enterprise.bell-bird.com.au.  1D IN A  192.168.1.1

You should deploy a split DNS or use some other method to block this from
the Internet.  A really thorough mail filter may be rejecting your mail
over this but I don't know of one that does.  Since you only have 2 nodes
and it won't change often you may just put these in your host file and pull
them out of your db files.


Good Luck,

Mike

--
Mike Ashcraft, Sr. Network Engineer
epixtech, Inc.
M.Ashcraft at epixtech.com



                                                                                                                    
                    Luke Vogel                                                                                      
                    <luke at bell-bir        To:     comp-protocols-dns-bind at moderators.isc.org                        
                    d.com.au>             cc:                                                                       
                    Sent by:              Subject:     Sendmail/DNS interaction problem.                            
                    news at nswpull.t                                                                                  
                    elstra.net                                                                                      
                                                                                                                    
                                                                                                                    
                    08/23/00 04:30                                                                                  
                    AM                                                                                              
                    Please respond                                                                                  
                    to luke                                                                                         
                                                                                                                    
                                                                                                                    





I have a simple home lan setup (1 linux pc - internet gateway + win98
pc)
I'm running BIND 8.2.2_p5 and sendmail 8.9.3-20

To a small number of addresses on the net, I cant seem to send e-mail. I
receive a
mail log entry as follows:
stat=Deferred: 451 <luke at bell-bird.com.au>... Sender domain must resolve

This only happens to a very small number of addresses ...
The good people on the comp.mail.sendmail newsgroup believe that the
problem is a DNS problem, or a DNS+sendmail integration problem.

This has me totally confused;
1.   becasue it only appears to happen to 2 ISPs that I'm aware of,
2.   The recipient is unable to send mail back to me.
3.   I regularly receive mail from all over the world.

So, if this is a DNS problem,

1.   Can anyone recommend a good set of diagnostic tools for sorting out
the config problems.
2.   A good on-line reference for explaining how the dns works
3.   Perhaps even a site with some clear examples of dns configuration
files.

I hate to ask questions in news groups without some understanding of the
topic, but I am finding good documentation hard to come by.

All sugestions would be appreciated.

TIA
--
Regards
Luke
PLEASE NOTE: Spamgard (tm) installed.
----
When the only tool you own is a hammer,
all problems begin to resemble nails.
----
http://www.bell-bird.com.au
mailto:luke at bell-bird.com.au
----








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