Pkg exim4 users - Aug 2009 - Configuring smarthost based on the network

Hi everyone,

(please Cc)

I guess that has been asked before, but I couldn''t find any answer,
which
is strange since I guess many people have to fight with that:

I am working on a laptop and switching networks permanently, from 
University to home (cable modem) to hotspots to wwan access.

All of these logins usually force me to use a different smart host for
sending emails.

Most of the times I just circumvent that by fixing one smart host 
(at the university) together with user authentication so that I can send
from anywhere in the world via that smart host.

Unfortunately sometimes the port 25 is blocked (even outgoing) in some
networks and smtp sending can *only* be done via their mail router.

Now, is there a solution to the changing smart host problem?

Best would be a solution that incorporates with e.g. wicd (which I am
using), or NetworkManager (which I never touched), and of course with
/etc/network/interfaces.

Thanks a lot for any suggestion and all the best

Norbert

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Dr. Norbert Preining <preining at logic.at>        Vienna University of
Technology
Debian Developer <preining at debian.org>                         Debian
TeX Group
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Polite word for buggery.
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Norbert Preining wrote:
> Hi everyone,
> 
> (please Cc)
> 
> I guess that has been asked before, but I couldn''t find any
answer, which
> is strange since I guess many people have to fight with that:
> 
> I am working on a laptop and switching networks permanently, from 
> University to home (cable modem) to hotspots to wwan access.
> 
> All of these logins usually force me to use a different smart host for
> sending emails.
> 
> Most of the times I just circumvent that by fixing one smart host 
> (at the university) together with user authentication so that I can send
> from anywhere in the world via that smart host.
> 
> Unfortunately sometimes the port 25 is blocked (even outgoing) in some
> networks and smtp sending can *only* be done via their mail router.
> 
> Now, is there a solution to the changing smart host problem?
> 
> Best would be a solution that incorporates with e.g. wicd (which I am
> using), or NetworkManager (which I never touched), and of course with
> /etc/network/interfaces.
> 
> Thanks a lot for any suggestion and all the best
These days it is common for people who run mail servers that relay, to 
listen on port 587 as well as port 25 to deal with exactly this problem. 
587 has become the mail submission port. See the RFC description here: 
http://www.ietf.org/rfc/rfc2476.txt

If your smtp relay isn''t listening on port 587 already, you could 
perhaps ask your IT department to add it?

-- 
Mike Cardwell - IT Consultant and LAMP developer
Cardwell IT Ltd. (UK Reg''d Company #06920226) http://cardwellit.com/

On 10 Aug 2009, at 01:21, Norbert Preining wrote:
> Unfortunately sometimes the port 25 is blocked (even outgoing) in some
> networks and smtp sending can *only* be done via their mail router.
Blocking port 25 is absolutely best practice.
Your MUA or MSA (if you are using exim in this sort of config), should  
instead be connecting to the MSA port (587) using an authenticated  
(and probably encrypted) session.  587 should be universally allowed  
through.

If your mail provider does not provide an MSA service on 587 then they  
are incompetent.  Beat them until they do.

	Nigel.

--
[ Nigel Metheringham             Nigel.Metheringham at InTechnology.com ]
[ - Comments in this message are my own and not ITO opinion/policy - ]

On Mon, Aug 10, 2009 at 02:21:55AM +0200, Norbert Preining
wrote:
> Unfortunately sometimes the port 25 is blocked (even outgoing) in some
> networks and smtp sending can *only* be done via their mail router.
> 
> Now, is there a solution to the changing smart host problem?
> 
> Best would be a solution that incorporates with e.g. wicd (which I am
> using), or NetworkManager (which I never touched), and of course with
> /etc/network/interfaces.
If you have an /etc/network/interface entry per network, you just add
an "exim4-smarthost" setting in the stanza and use this
/etc/network/if-up.d/exim4-smarthost:

#!/bin/bash

# Environment:
#  MODE = { start | stop }
#  IF_EXIM4_SMARTHOST = hostname port

SMARTHOSTFILE="/etc/exim4/conf.d/main/00_local_DCsmarthost"

if [ -z "$IF_EXIM4_SMARTHOST" ]; then
  exit 0
fi

if [ "$MODE" = ''stop'' ]; then
  rm -f $SMARTHOSTFILE
  /etc/init.d/exim4 reload > /dev/null || true
  exit 0
fi

if [ "$IF_EXIM4_SMARTHOST" = "none" ]; then
  rm -f $SMARTHOSTFILE
  /etc/init.d/exim4 reload > /dev/null || true
  exit 0
fi

echo "DCsmarthost = ${IF_EXIM4_SMARTHOST}" > $SMARTHOSTFILE

/etc/init.d/exim4 reload > /dev/null || true
/usr/sbin/exim4 -qqf


This works only with split config.

I didn''t find any Networkmanager docs which would allow me to
understand it, so I do not have a solution for this.

Greetings
Marc

-- 
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im Header
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Hi Marc,

On Mo, 10 Aug 2009, Marc Haber wrote:
> If you have an /etc/network/interface entry per network, you just add
> an "exim4-smarthost" setting in the stanza and use this
> /etc/network/if-up.d/exim4-smarthost:
Ahh thanks a lot, that helps already. I didn''t know what is the
relation between /e/n/interfaces stanzas and the files in /e/n/if-up.d/.

I had something similar with post-up or so, that tried to deduce
from the IP the correct smarthost and wrote it into a lsearch-able
file, but your solution is much better.
> I didn''t find any Networkmanager docs which would allow me to
> understand it, so I do not have a solution for this.
I will check with wicd what can be done there. Would be nice.

Again, thanks a lot and all the best

Norbert

-------------------------------------------------------------------------------
Dr. Norbert Preining <preining at logic.at>        Vienna University of
Technology
Debian Developer <preining at debian.org>                         Debian
TeX Group
gpg DSA: 0x09C5B094      fp: 14DF 2E6C 0307 BE6D AD76  A9C0 D2BF 4AA3 09C5 B094
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Things said on the spur of the moment to explain to someone who comes
into a room unexpectedly precisely what it is you are doing.
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On Mon, Aug 10, 2009 at 12:49:23PM +0200, Norbert Preining
wrote:
> On Mo, 10 Aug 2009, Marc Haber wrote:
> > If you have an /etc/network/interface entry per network, you just add
> > an "exim4-smarthost" setting in the stanza and use this
> > /etc/network/if-up.d/exim4-smarthost:
> 
> Ahh thanks a lot, that helps already. I didn''t know what is the
> relation between /e/n/interfaces stanzas and the files in /e/n/if-up.d/.
What you write in an interface stanze into /e/n/i, gets put
capitalized and IF_-prefixed in the environment of the scripts that
get called from /e/n/if-(pre-)?(up|down).d.

exim4-smarthost => IF_EXIM4_SMARTHOST.

Greetings
Marc

-- 
-----------------------------------------------------------------------------
Marc Haber         | "I don''t trust Computers. They | Mailadresse
im Header
Mannheim, Germany  |  lose things."    Winona Ryder | Fon: *49 621 72739834
Nordisch by Nature |  How to make an American Quilt | Fax: *49 3221 2323190