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#1 (**permalink**) 01-27-2008, 09:17 AM

Once apon a time I had a really good Exim4 configuration. It was more
arse than class, and I wouldn't have a clue how I did it, and where I
got the bits from that went into it. But I want to try and redo it.

Trouble is that last time I did try to do anything with my Exim4
configs, I was wondering where my system messages had dissapeared to,
when I got a polite email from some other customer on my ISP.

So, I'm wondering, how to safely test a new configuration before putting
it into action, and what corner cases to watch out for...

Fredderic

#2 (**permalink**) 03-07-2008, 02:28 PM

Fredderic wrote:
> Trouble is that last time I did try to do anything with my Exim4
> configs, I was wondering where my system messages had dissapeared to,
> when I got a polite email from some other customer on my ISP.

By "system messages", are you referring to the e-mail's that are
normally sent to root that are automatically generated by various
services to notify you of events?

> So, I'm wondering, how to safely test a new configuration before putting
> it into action, and what corner cases to watch out for...

Disconnect from the network and test local delivery. If my assumption
above is correct, do something that would trigger an event that would
automatically generate an e-mail that is sent to root (and this can be
redirected to a normal user account).

- Ken

#3 (**permalink**) 03-07-2008, 02:28 PM

On Thu, 06 Mar 2008 21:28:34 -0800,
Ken Teague <"kteague at pobox dot com"> wrote:

> Fredderic wrote:
>> Trouble is that last time I did try to do anything with my Exim4
>> configs, I was wondering where my system messages had dissapeared
>> to, when I got a polite email from some other customer on my
>> ISP.

> By "system messages", are you referring to the e-mail's that are
> normally sent to root that are automatically generated by various
> services to notify you of events?

Yeah... Change logs and the results from rkhunter and its ilk, aren't
really the sort of messages I want being sent out to some random user
on the internet.

>> So, I'm wondering, how to safely test a new configuration before
>> putting it into action, and what corner cases to watch out for...
> Disconnect from the network and test local delivery. If my
> assumption above is correct, do something that would trigger an event
> that would automatically generate an e-mail that is sent to root (and
> this can be redirected to a normal user account).

At present, I have all remote delivery disabled. At least until I have
the patience to try and figure it all out again.

It's also hard taking this system offline to test a new mail
configuration. Everyone else in the house starts screaming at me if I
do that, because the internet connection runs through my machine.

The only downside to this configuration, is that every month the linux
counter script tries to email home and shortly thereafter I get a bounce
message in my inbox. One day..... *chuckles*

Fredderic

#4 (**permalink**) 03-07-2008, 02:28 PM

Fredderic wrote:
> It's also hard taking this system offline to test a new mail
> configuration. Everyone else in the house starts screaming at me if I
> do that, because the internet connection runs through my machine.

You can use netfilter to setup a firewall rule (using iptables) to block
outgoing connections via port 25 (the SMTP port). It's been forever and
a day since I've done anything with netfilter, so I would suggest taking
a look at their NAT documentation at:
http://www.netfilter.org/documentati...NAT-HOWTO.html

If you have issues figuring it out, let us know and we'll do what we can
to help out.

> The only downside to this configuration, is that every month the linux
> counter script tries to email home and shortly thereafter I get a bounce
> message in my inbox. One day..... *chuckles*

After you setup your netfilter rule, test your configuration
immediately. Then, after you're satisfied with your results, remove the
rule and immediately test an outgoing e-mail to an external webmail
account. I wouldn't suggest yahoo webmail as a good alternative since
their SMTP servers seem to be slow on delivery a lot of the time.

- Ken

#5 (**permalink**) 03-07-2008, 02:28 PM

On Thu, 06 Mar 2008 23:30:34 -0800,
Ken Teague <"kteague at pobox dot com"> wrote:

> Fredderic wrote:
>> It's also hard taking this system offline to test a new mail
>> configuration. Everyone else in the house starts screaming at me
>> if I do that, because the internet connection runs through my
>> machine.
> You can use netfilter to setup a firewall rule (using iptables) to
> block outgoing connections via port 25 (the SMTP port).

heh That's a point... And very easy to do. Hadn't thought about it,
though. Thanks for the idea.

It's going through the documentation and figuring out what to stick
where, that's the hard part.

Out of curiosity, I'm wondering which people prefer; the Exim
configuration all in one piece, or individual files?

Fredderic

#6 (**permalink**) 03-07-2008, 02:28 PM

Fredderic wrote:
> It's going through the documentation and figuring out what to stick
> where, that's the hard part.

It depends on the arguments passed to exim when it's started. See:
http://www.exim.org/exim-html-curren...html/ch03.html
.... look at section "3.5 Receiving mail". I think you would want to
insert your rule at the top of the rule stack (-I option for iptables)
to ensure it's one of the first rules that are processed before any
other rule that may end up processing it and letting it through.

> Out of curiosity, I'm wondering which people prefer; the Exim
> configuration all in one piece, or individual files?

I think for most simple setups, people prefer a single config file.

- Ken

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Safely test an Exim4 configuration