Mailing List Archive: exim: users

Lookup domain before delivery

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thierry at 8p-design

Mar 4, 2010, 11:58 AM

Post #1 of 3 (347 views)
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Lookup domain before delivery

Hi,

I would like exim to verify that the domain DNS **really** resolves to the
local computer before delivering locally.

Example (very far fetched example): if say I set a hotmail.com domain on my
machine it will deliver any xyz [at] hotmail message locally without
verifying the real DNS setup. So the real xyz [at] hotmail user will never
receive the message.

QUESTION: Is there a way to tell exim to lookup the domain before delivery?

thanks for your help.

note: we setup domains on our server that are not yet moved or for testing
reasons...

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peter at bowyer

Mar 5, 2010, 12:33 AM

Post #2 of 3 (343 views)
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Re: Lookup domain before delivery [In reply to]

On 4 March 2010 19:58, Thierry Lavallee <thierry [at] 8p-design> wrote:
> Hi,
>
> I would like exim to verify that the domain DNS **really** resolves to the
> local computer before delivering locally.
>
> Example (very far fetched example): if say I set a hotmail.com domain on my
> machine it will deliver any xyz [at] hotmail message locally without
> verifying the real DNS setup. So the real xyz [at] hotmail user will never
> receive the message.
>
> QUESTION: Is there a way to tell exim to lookup the domain before delivery?

Exim's view of 'reality' is determined entirely by the routers you
configure and the order in which you place them in the config file. If
you have a router that resolves a domain by DNS before one that
resolves the same domain as local, then behaviour will be as you
intend.

If you have a config derived from the one that came with your Exim
distribution, you may be able to make this happen by removing the
domain in question from the 'local_domains' domainlist. Otherwise you
need to adjust your routers by hand.

Peter

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Peter Bowyer
Email: peter [at] bowyer
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jh at plonk

Mar 5, 2010, 12:55 AM

Post #3 of 3 (343 views)
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Re: Lookup domain before delivery [In reply to]

Thierry Lavallee, 2010-03-04 20:58:

> Example (very far fetched example): if say I set a hotmail.com domain on my
> machine it will deliver any xyz [at] hotmail message locally without
> verifying the real DNS setup. So the real xyz [at] hotmail user will never
> receive the message.
>
> QUESTION: Is there a way to tell exim to lookup the domain before delivery?

Sure. How to do it totally depends on your router configuration,
especially the order.

Exim's default config has a dnslookup router listed as the first one. If
you remove the "domains = ! +local_domains" line and add "self = pass",
it should work.

If you have the router for your local domains before the one for remote
domains, you could probably use the dnslookup router instead of the
accept router for your "localuser" and use "self = send" on it. (Don't
know if that works, though).

Both approaches depend on stable dns resolving, so you should take care
of that. Exim defers the address on dns timeouts by default, so it's
probably not that critical.

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