Re: Configuring Exim for mail delivery

From	Brian <ad44@cityscape.co.uk>
Newsgroups	linux.debian.user
Subject	Re: Configuring Exim for mail delivery
Date	2016-10-01 16:40 +0200
Message-ID	<sntCi-1jD-13@gated-at.bofh.it> (permalink)
References	(1 earlier) <snhKO-1ya-1@gated-at.bofh.it> <snpS2-7al-23@gated-at.bofh.it> <snrAu-8pp-7@gated-at.bofh.it> <sns3v-97-1@gated-at.bofh.it> <snsGe-D4-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Sat 01 Oct 2016 at 22:36:09 +0900, Mark Fletcher wrote:

> On Sat, Oct 01, 2016 at 01:56:40PM +0100, Brian wrote:
> 
> > 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.
> > 

I hope we are not talking at cross-purposes. I was explicitly addressing
the issue of why an entry in /etc/hosts for machines on the network will
not replace a hubbed_hosts file.

> With great respect I think that confuses the issue. A DNS lookup will 
> *not* explicitly get done by exim4 if the target domain is in 
> hubbed_hosts, or if exim4 has been told it is the local domain. The 

A hubbed_hosts file is for overriding or augmenting MX information from
the DNS (exim4-config_files). If you had

  lists.debian.org: 91.221.168.152

the DNS would not be used and any mail to debian-user@lists.debian.org
would go to 91.221.168.152. MX information would be overriden.

With

  server: 192.168.5.100 or server: server.local

MX information is augmented.

> point is one wishes to PREVENT a DNS lookup that is doomed to fail, and 

No. The point is you want to override or augment MX information. Ok, a
DNS lookup is prevented but it is not because it is one which is doomed
to fail. A lookup on lists.debian.org would succeed but for some reason
the user wants the mail to go to 91.221.168.152.

> one does so for machines that are not the machine-local domain by 
> putting them in hubbed_hosts, which will cause exim4 to throw out a 
> connection request for the local network infrastructure (starting with 
> the network infra on the local machine) to handle, without doing an 
> explicit DNS lookup. That is handled by /etc/hosts if it is populated, 
> and by Avahi if it is present and /etc/hosts is not populated, and no 
> doubt by a few other alternatives I am not familiar with as well. If 
> none of them succeed, the delivery will fail, because if I recall 
> correctly hubbed_hosts router config ends with no_more which prevents 
> other routers having a go.

exim does not use /etc/hosts; user@server will fail with '192.168.7.88
server' in it. user@server,local succeeds because server.local is in the
DNS.

-- 
Brian.

Thread

Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-09-30 22:30 +0200
  Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-01 00:50 +0200
  Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 04:00 +0200
    Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 12:40 +0200
      Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 13:30 +0200
        Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 13:50 +0200
          Re: Configuring Exim for mail delivery Clive Menzies <clive@clivemenzies.co.uk> - 2016-10-01 14:00 +0200
            Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:10 +0200
          Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:10 +0200
          Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 14:10 +0200
      Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 14:30 +0200
        Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:40 +0200
          Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 15:00 +0200
            Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 15:00 +0200
        Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 15:00 +0200
          Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 15:10 +0200
          Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 15:40 +0200
            Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 16:20 +0200
            Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 16:40 +0200
      Re: Configuring Exim for mail delivery Teemu Likonen <tlikonen@iki.fi> - 2016-10-01 16:00 +0200
        Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 16:20 +0200
  Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 11:10 +0200
    Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 12:10 +0200
      Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 12:40 +0200
      Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:10 +0200
        Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 14:30 +0200
          Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:30 +0200
            Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 15:00 +0200
              Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 15:10 +0200
      Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 14:10 +0200
    Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-01 13:40 +0200
      Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 14:10 +0200
    Re: Configuring Exim for mail delivery rhkramer@gmail.com - 2016-10-01 14:20 +0200
      Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 16:30 +0200
    Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-01 18:30 +0200
      Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-01 20:20 +0200
        Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 22:50 +0200
          Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-02 00:30 +0200
            Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-02 02:30 +0200
              Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-02 13:10 +0200
            Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-02 10:50 +0200
        Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-01 23:10 +0200
          Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-02 00:40 +0200
            Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-02 02:10 +0200
              Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-02 14:00 +0200
                Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-02 14:50 +0200
                Re: Configuring Exim for mail delivery Gene Heskett <gheskett@shentel.net> - 2016-10-02 15:20 +0200
                Re: Configuring Exim for mail delivery Mark Fletcher <mark27q1@gmail.com> - 2016-10-02 15:50 +0200
                Re: Configuring Exim for mail delivery Brian <ad44@cityscape.co.uk> - 2016-10-02 15:40 +0200
                Re: Configuring Exim for mail delivery Liam O'Toole <liam.p.otoole@gmail.com> - 2016-10-02 17:30 +0200
      Re: Configuring Exim for mail delivery mo <mo777@gmx.net> - 2016-10-01 22:50 +0200

csiph-web