Re: [exim] Which interface is used at remote_smtp transport?

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Author: Dave Evans
Date:  
To: Marten Lehmann
CC: exim-users
Subject: Re: [exim] Which interface is used at remote_smtp transport?
On Tue, Feb 22, 2011 at 07:15:21PM +0100, Marten Lehmann wrote:
> Hello,
>
> I wonder why Exim is using arbitrary interfaces so send mail from.


Because your config doesn't specify which interface to use, so it uses the
kernel's choice, which may seem to you to be arbitrary (and it may even be
so).

> Our remote_smtp transport on our webservers is pretty simple:
>
> remote_smtp:
>     drive = smtp

>
> I know that it is possible to specify an interface address, but we don't
> want to do this, because the configuration shall be identical on all
> webservers.


But the implication of your question is that you /do/ care what interface is
used, so therefore you /do/ want to specify which interface to use.

> Does exim rely on the operating system


Yes, unless you tell it what address to bind to.

It sounds like you want to:

- specify which address to bind to ("interface"), at least some of the time
- using some logic or other, that you haven't discussed here (fine)

- keep your config identical across your servers

Those goals /might/ not be incompatible - it all depends on what the
as-yet-unknown logic is that you want to use to select the bind address.
Without knowing more about that I'm not sure what else to suggest, other than
pointing out that:

(a) "interface" is expanded before use, so you've got the
full power of lookups etc at your disposal; and

(b) you might find it useful to split your config into two or more files,
(say) "exim.conf" (common to all servers) and that .include's (say)
"local.conf" (individual to each server); and perhaps all that's in
that file is a macro or two.

--
Dave Evans
http://djce.org.uk/
http://djce.org.uk/pgpkey