[Exim] Re: Problem with exim on internal network

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Autor: Rob Borland
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A: exim-users
Assumpte: [Exim] Re: Problem with exim on internal network
> Date: Sat, 3 Jan 2004 23:08:46 +0100
> From: Christian Schmidt <ChriSchmiLi@???>
> To: exim-users@???
> Subject: [Exim] Re: Problem with exim on internal network


> Hello syn,


> syn uw, 03.01.2004 (d.m.y):


>> We are running EXIM on Linux on an internal web server running on a internal
>> private network (hidden by NAT). EXIM is only responsible for sending out
>> mails from our webmail system. The problem that we are encountering is when
>> we are sending mails to domains that are hosted on our server: EXIM does an
>> MX lookup for a domain hosted on our servers and then gets the external IP
>> address of that our server and not the internal address. I tryed to force
>> this by entering our mail server host's internal IP in /etc/hosts but still
>> it takes the external address.


> Yes, that's because the DNS lookup is done by exim: exim does _not_
> only aks for the A record of your email server (its IP address).
> What exim asks for is (probably) the MX record, i.e. your MTA wants to
> know which server the DNS considers as your domain's Mail Exchanger
> (MX).


>> Thus mails get undelivered as from the
>> internal network it's not posible to use external IP addresses (that's how
>> our OpenBSD firewall works).
>>
>> Does anyone have an idea ?


> Just define an additional router in your exim.conf that redirects mail
> to <anyone@???> just to the corresponding machine.
>
> Just take a closer look at the exim specs, all you need is mentioned
> there.
>
> Regards,
> Christian


I've been looking for exactly this function. I've read the specs but I can't
find this described.

I'm preparing to convert from sendmail where the following entry in mailertable
routes to the host's A address rather than MX address:

  host.domain.example       esmtp:[target.host.example]


I'd appreciate it if you could give an example of how and where to define this
router or a pointer to the docs which describe this.

Regards,
Rob