Re: Configuring Exim for mail delivery
On Sat 01 Oct 2016 at 21:23:33 +0900, Mark Fletcher wrote:
> On Sat, Oct 01, 2016 at 12:36:10PM +0200, mo wrote:
> >
> > I just did that and now mailing works flawlessly :D
> > Just one questions: Why do i need hubbed_host entries? Should it not be fine
> > alone to make a entry in /etc/hosts for the machines i want to send mail to
> > (I do not operate a dedicated DNS server).
> > This is something i dont really understand...
>
> hubbed_host entries apply only to exim4. I also suspect, but am not
> sure, that they are a Debian extension to exim4 in the sense that the
> *DEBIAN* exim4 comes configured for them out of the box, while the
> upstream exim4 does not. IIRC there is no reference to hubbed_hosts in
> the upstream documentation, only in the Debian docs.
Correct. I'll add: the upstream documentation spec.txt.gz covers
hubbed_hosts in sections 20.3 to 20.7. It is not obligatory to read it.
> They work because the debian config contains a router to handle hubbed
> hosts. You can see what it is doing if you search
> /var/lib/exim4/config.autogenerated for the text hubbed_hosts.
Fine.
> If the file is not populated this router is skipped and then exim4
> requires either that the address is the local machine, or that there is
> a smarthost configured that it can delegate to, or that it can find an
> official MX entry for the target domain by doing a DNS lookup. All of
> which will fail for a local box that isn't registered to the world as a
> mail server.
The thing for Mo to grasp is that exim *always* does an MX lookup, often
using the ISP's DNS server. user@server will fail (as has been found
out) because the domain "server" is not in the DNS.
/etc/hosts is not consulted when the lookup is done. exim can be made to
look at /etc/hosts but for such a simple setup it is not worth the
effort and would likely lead to a world of pain.
--
Brian.
Reply to: