Re: Exim and hostname --fqdn, was Re: mutt attachment error

[Brian <ad44@cityscape.co.uk>]

On Tue 17 May 2016 at 12:32:33 -0500, David Wright wrote:

> On Thu 12 May 2016 at 20:38:41 (+0100), Brian wrote:
> 
> > For Exim and minimaldns the question is
> > 
> >   Does the hostname resolve to a fqdn (something with a dot in it)?
> > 
> >  127.0.1.1       alum.anything_you_want		alum
> > 
> > would do this.
> 
> I haven't worked out why exim needs hostname --fqdn to resolve to a
> dotty name. After all, it knows that your desktop.lan isn't really a
> routable internet address just by its IP number.

I'm not too sure being a routeable address is of significance to Exim.
If it isn't, I do not know why.

I'm going to stick with the advice to have a fqdn in /etc/hosts. It
works for me with Exim.

 http://lists.alioth.debian.org/pipermail/pkg-exim4-users/2008-April/001328.html

   I am very reluctant to give a "Unix administration course" in a
   warning printed by an arbitrary tool. This usually leads to people not
   reading the text because it's longer than two lines.

   The correct answer would of course be "have an FQDN in the 127.0.1.1
   line in /etc/hosts" for the majority of Debian systems.

 http://lists.alioth.debian.org/pipermail/pkg-exim4-users/2008-April/001326.html

   dc_minimaldns works by virtue of hardcoding the output of "hostname
   --fqdn" into the primary_hostname configuration option by
   update-exim4.conf, thus at package configuration time.
   update-exim4.conf silently does not set primary_hostname if hostname
   --fqdn's output does not at least contain one dot, effectively
   rendering dc_minimaldns invalid.

I think primary_hostname is at the root of this.

> > Having said this it as well to realise Exim will HELO to a remote host
> > with "alum.anything_you_want". Some misguided hosts will deny contact
> > because there is no reverse lookup which satisfies them. ISP smarthosts
> > are generally very forgiving (they have to be!) so this is generally not
> > a problem with sending mail through them.

> That issue is covered by setting helo_data, which has the advantage
> that it can be evaluated at the time it's used, so you can tailor it
> to each and every host you use.

Tried this in the past. It worked. Having no need for tailoring I
returned to using /etc/hosts for the HELO.