Re: [Exim] DNS MX Error

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Author: Greg Ward
Date:  
To: Paulo Henrique Baptista de Oliveira
CC: exim-users, suporte
Subject: Re: [Exim] DNS MX Error
On 13 October 2001, Paulo Henrique Baptista de Oliveira said:
> Server A has a permanent Internet connection and can deliver to
> telemar-rj.com.br:

[...]
> Server B has a DSL Internet connection and can't deliver to
> telemar-rj.com.br:
>
> internet:~# exim -bt user@???
> user@??? is undeliverable:
> all relevant MX records point to non-existent hosts
>
>     I checked Server A and B exim.conf against one to other and cant find
> the solution! :(


Then it's probably a DNS problem, not an Exim problem.

Do A and B use the same DNS setup?

Use DNS utilities like "dig" or "host" to figure this out. Here's what
I get on my machine poking around the mail-related DNS for your domain:

  $ host -t MX telemar-rj.com.br
  telemar-rj.com.br       MX      1 mailgwo01.telemar.com.br
   !!! telemar-rj.com.br MX host mailgwo01.telemar.com.br is not canonical
  telemar-rj.com.br       MX      0 mailgwi01.telemar.com.br
   !!! telemar-rj.com.br MX host mailgwi01.telemar.com.br is not canonical


[Oops, found one problem with your DNS already]

  $ host mailgwo01.telemar.com.br
  mailgwo01.telemar.com.br        CNAME   mailgwo01.informatica.telerj.net.br
  mailgwo01.informatica.telerj.net.br     A       200.222.3.157


  $ host mailgwi01.telemar.com.br
  mailgwi01.telemar.com.br        CNAME   mailgwi01.informatica.telerj.net.br
  mailgwi01.informatica.telerj.net.br     A       200.222.3.109


MX records are not supposed to point to CNAME records. Some MTAs can
probably deal with this, some probably can't. I would guess that Exim
can, but I don't know for sure.

Now let's see if those MXs are working:

$ telnet 200.222.3.157 25
Trying 200.222.3.157...
[...sits there forever...]

$ telnet 200.222.3.109 25
Trying 200.222.3.109...
Connected to 200.222.3.109.
Escape character is '^]'.
220 mailgwi01.rj.telemar ESMTP Server (Microsoft Exchange Internet Mail Service 5.5.2653.13) ready

Ooh, that's bad: one of your MXs isn't responding. It's your
lower-priority MX, so this won't become a problem until your
higher-priority MX goes down. Careful!

Anyways, do stuff like this from the host that's having problems.
Should be pretty clear before long what's going wrong.

        Greg
-- 
Greg Ward - software developer                gward@???
MEMS Exchange                            http://www.mems-exchange.org