[nzlug] Understanding email DNS

[Warren Boyd]

On 2006-10-05, at 10:55 , Michael Adams wrote:

>
> I need a little help understanding how email DNS works.
>
> At work we have web sites with a couple of different crowds. The
> national ones are hosted with a web developer on e-Xpert accounts that
> are mainly designed to be websites only. Our regional ones i have  
> set up
> with IServe through kiwiwebhost.co.nz running on LAMP servers.
>
> The simple story is IServe will let me have add on domains as good as
> gold. e-Xpert has the domains; foo.org.nz and eastcoast.foo.org.nz.
>
> I was under the impression that the email for these domains had to
> go through e-Xperts mailserver. Yet one of the other regions tells me
> that their northern.foo.org.nz emails come direct to their server.


DNS MX records handle this - what the MX record essentially does is  
say "this mail server is responsible for email for this domain"

So, northern.foo.org.nz is possibly already pointing at the "northern  
server"

Your domains at iserve are already setup to point to iserve's mail  
servers.

>
> Either it is being forwarded through to this second server or there is
> some other jiggery-pokery going on that i haven't heard of. Anyone  
> want
> to explain in laymans terms what might be going on here?

The email is probably handled via one of the following:
* forwarded directly onto the "northern server"
* multi-drop mailbox, with the "northern server" picking up the mail
* the "northern server" is the mail handler

>
> I couldn't get hold of the tech at the northern end to let him explain
> it to me. He was on the road to Wellington.
>

Check the mx records:

"dig northern.foo.org.nz mx"

The output will tell you where the mail is due to go.

Hrmmm ... I hope that helps point you a little further down the  
track ...

Cheers,
Warren.