Re: [exim] Consider local_domains only if DNS matches

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Autor: Phil Pennock
Data:  
Para: Peter Thomassen
CC: exim-users
Assunto: Re: [exim] Consider local_domains only if DNS matches
On 2007-05-15 at 23:24 +0200, Peter Thomassen wrote:
> I'm sorry, but I have found cases in which these routers don't work. Usually
> there is something specified like:
>
>         example.org     MX 10   mail.a4a.de

>
> Now I found that all subdomains of example.com are broken regarding e-mail;


An MX record for example.org says *nothing* about sub-domains.
Properly, you need MX records for them all; this has been true for a
long time, but there's backwards-compatibility for "the days before MX
records" in the SMTP routing spec, which says that an A record will be
looked for if there are no MX records.

I alluded to this with:
----------------------------8< cut here >8------------------------------
If your customers can end up with an A record for the domain pointing to
your system and no MX records then this won't be sufficient and you'll
need to add a lot more complexity.
----------------------------8< cut here >8------------------------------
when I was talking about the manual approach.

In my previous email, I pointed out that "self = pass" is necessary; in
the first mail, I mentioned it only to in connection with having to
set hosts_treat_as_local for a cluster for "self = pass" to work
properly.

> R: dnslookup_not_yet_hosted for info@???
> LOG: MAIN
> remote host address is the local host: sub.example.org (while routing <info@???>)
> info@??? cannot be resolved at this time:
> remote host address is the local host


"self = pass" fixes this, letting it continue on.

> Why isn't that passed on to the local routers? Do I have to set up MX
> records for *.example.org?


A DNS RR for "*.example.org" will only supply data for those labels
which don't already have RRs; if you have an A record for
sub.example.org then "*.example.org MX 10 foo.example.org." won't
generate an MX response for "sub".

Yes, anything which is a mail domain in a supported email address should
have MX records. If you're relying on A record fallback, you need "self
= pass".

See my mail:
Message-ID: <20070515182233.GA98683@???>

Regards,
-Phil