Re: [exim] how to smtp bet 2 NAT'd LAN hosts when RFC 3330 e…

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Author: Tony Finch
Date:  
To: OpenMacNews
CC: exim-users
Subject: Re: [exim] how to smtp bet 2 NAT'd LAN hosts when RFC 3330 exclusions are in place?
On Tue, 20 Sep 2005, OpenMacNews wrote:
>
> i've 2 mail servers on the same MAT'd LAN:
>
> primary domain       listener IP     machine LAN name
> mail.domain1.com      10.0.0.1       box1.mydomain.com
> mail.domain2.com      10.0.0.2       box2.mydomain.com

>
>     dnslookup:
>         driver                  = dnslookup
>         domains                 = !+local_domains
>         ignore_target_hosts     = +rfc3330_hosts
>         same_domain_copy_routing
>         no_more
>         cannot_route_message    = Invalid domain part in email address
>         transport               = remote_smtp

>
> this -- seemingly -- prevents the delivery from 'mail.domain1.com' to
> 'mail.domain2.com' using the dnslookup router.
>
> what's the cleanest way to deal with this?


In general you should not put MX records in the (public) DNS which refer
to RFC 3330 IP addresses. This kind of setup requires private email
routing arrangements.

What we do in Cambridge is have the MX records for most of our domains
pointing to mx.cam.ac.uk, with a manualroute table to handle routing to
internal email servers. The dnslookup router isn't used for these domains,
so our RFC 3330 restrictions don't apply.

In most cases, all of the addresses involved are public (though they may
be firewalled off). We also have a private DNS setup for our 172.16.0.0/12
private network. This private DNS doesn't have any MX records in it - they
are all public. Two departments have their email servers on private
addresses, and the same manualroute setup is used to deliver email to
them, without any special considerations.

Tony.
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