imlinterconnect.net wrote:
>
> I am wondering if DNS will always override transport.

No, not at all.

> For example, say I have the following DNS setup (this isn't real dns
> format it is just so you can see the relavent info).
>
> box.domain.com 192.168.0.1
> mx 10 box.domain.com
> mx 20 mail2.otherdomain.com
>
> mailhub.domain.com 192.168.0.2
>
> domain.com 192.168.1.1
> mx 10 mailhub.domain.com
> mx 20 mail2.otherdomain.com
>
> mail.domain.com 192.168.1.2
> mx 10 mailhub.domain.com
> mx 20 mail2.otherdomain.com
>
> now postfix is on box.domain.com (which is also mailhub.domain.com, I
> know this may be questioned but it is aside from the point). This is
> the following relavent postfix config:
>
> myhostname = mailhub.domain.com
> mydestination = domain.com, mail.domain.com
> transport_maps = hash:/usr/local/etc/postfix/transport
>
> Here is where I run into the problem. If I put the transport as
> follows:
>
> domain.com :mail.domain.com
>
> Then it messages will bounce saying it is pointing back to itself. I
> suspect it is following strict DNS rules. If I put it as follows:
>
> domain.com :[192.168.1.2]
>
> Then it works fine. So the real question I guess is just trying to
> see on a lower level how postfix is working. It appears to be taking
> the MX record over the transport file.

When you use

 domain.com smtp:some.machine.name

postfix will lookup some.machine.name in DNS, looking to MX records, and if
not found, A records. If you use

 domain.com smtp:[some.machine.name]

or, like in your case,

  domain.com smtp:[ip.add.re.ss]

postfix will lookup A record only (for name, not for ip.add.re.ss). This
is documented. (Note that empty transport name means $default_transport;
and this particular interpretation of transport definition is specific
to smtp transport; for other transports, semantic and interpretation will
be different).

> Part 2 of this question is how do I make the headers show
> mailhub.domain.com when it talks to other servers. Right now it shows
> a little something like:
>
> Received: from mailhub.domain.com [192.168.0.1] by ....

This is what 192.168.0.1 tells in HELO:

 HELO mailhub.domain.com [192.168.0.1]

(this is syntactically incorrect). Format of postfix's Received line
for smtpd looks like:

 Received: by HELO (hostname [ip.add.re.ss])
    by $myhostname ...

the HELO part is exactly what smtp client said. Fix your software that
talks to postfix I'd say.

For example, I disallow any invalid helo arguments entirely here, so
if such client will talk with my postfix, it will never able to send
mail at all.

Regards,
 Michael.
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