[nzlug] Understanding email DNS

[Michael Adams]

On Thu, 05 Oct 2006 23:45:28 +1300
Robin Sheat wrote:

> On Thursday 05 October 2006 22:55, Michael Adams wrote:
> > 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.
> It does whatever it's been told to do, basically. 
> 
> When an email it to be delivered, the server looks up the hostname
> (e.g. eastcoast.foo.org.nz), finds the MX (Mail eXchange) record (e.g.
> mail.foo.org.nz) and sends the mail to that. If you added another
> subdomain (e.g. northern.foo.org.nz) and set the MX record to
> something else (e.g. kallisti.hopto.org), then all the mail
> @northern.foo.org.nz would go via my mail server (and bounce, but
> that's beside the point:)
> 
> To find out the MX records, do this:
> $ host -t MX kallisti.net.nz
> kallisti.net.nz mail is handled by 15 mail2.umbra.net.nz.
> kallisti.net.nz mail is handled by 5 kallisti.hopto.org.
> kallisti.net.nz mail is handled by 10 smtp.umbra.net.nz.
> 
> The numbers are the priority, lowest to highest, specifying the order
> the servers get tried in. If you compare the results of that command
> on eastcoast.foo.org.nz and northern.foo.org.nz, I expect you'll get a
> different result. Also note that the MX record is just a line in a
> file somewhere, so it can be changed to point whereever you like,
> typically at the most convenient mailserver, and some backups.
> 

So the MX hostname at the domain hosts DNS (e-Xpert) needs to be pointed
to a mail server of my choosing (Iserve) for eastern.foo.org.nz. This
would replicate what norhtern are doing, correct?

graphically
*********
(e-Xpert)
foo.org.nz
     |
     - northern.foo.org.nz MX --> mail.nth.org.nz
     - eastern.foo.org.nz MX --> mail.bar.org.nz
     - others.foo.org.nz

(Iserve)
bar.org.nz (which we own)
     |
     -mail.bar.org.nz <-- eastern.foo.org.nz
*********

Can the mail be pointed to a server mail.bar.org.nz as above?
If so:
 . Will our foo group be able to use eastern.foo.org.nz email addys?
 . What do i ask e-Xpert to set up at their end?
 . What do i ask Kiwiwebhost(Iserve) to set up their end?
 

-- 
Michael
 Those that can, do; those that can't, teach.