Re: [exim-dev] tls_sni = $host in default configuration file

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Author: Andreas Metzler
Date:  
To: exim-dev
Subject: Re: [exim-dev] tls_sni = $host in default configuration file
On 2018-12-17 Phil Pennock via Exim-dev <exim-dev@???> wrote:
> On 2018-12-16 at 10:42 +0000, Jeremy Harris via Exim-dev wrote:
> > On 16/12/2018 10:20, Andreas Metzler via Exim-dev wrote:
> > > 4.92rc1 adds this to the smarthost_smtp transport:
> > >
> > > tls_sni = $host
> > >
> > > I do not think that always works as expected. Depending on the DNS setup
> > > (CNAME, round robin) $host will not contain the name of the selected
> > > smarthost anymore but a different value.

[...]
> I think that I just missed that we might adapt `$host` during the life
> of the Transport.


> <https://www.exim.org/exim-html-current/doc/html/spec_html/ch-the_smtp_transport.html>
> 30.2


> Absent `hosts_override` or `hosts` directly on the Transport, Round
> Robin A records have no cause to change the host _name_. So the only
> issue should be CNAME records?

[...]

Hello Phil,

I only recognized the problem because we have had to workaound/document
around it in Debian for ages. - We have been using ${lookup{$host} in
smtp authentication.

CNAME for smarthost is very common, the biggest players (office365,
gmail and yahoo) use it.

cu Andreas

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