Re: [Exim] 'Unrouteable mail domain'/sporadic MX lookup fail…

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Author: Philip Hazel
Date:  
To: Adam Newby
CC: Greg A. Woods, exim-users
Subject: Re: [Exim] 'Unrouteable mail domain'/sporadic MX lookup failures
On Tue, 8 Apr 2003, Adam Newby wrote:

> Retrying on an MX lookup failure, as far as I know, would not break any
> rules, and would only involve extra work on the part of our mail server
> and not that of others.


This behaviour may get you out of your current problem, but it is fixing
the symptom, and not the disease, and furthermore it would be doing so
in a particularly bad way.

Let me put another idea (which just came to me) to you:

When a dnslookup router fails to find an address in the DNS, it declines
- the address is then passed on to the next router. You can trivially
add this router:

delay_and_retry_if_no_mx:
driver = redirect
domains = !+local_domains
allow_defer
data = :defer: deferred because dnslookup declined

Put it *after* the dnslookup router, and remove the "no_more" setting on
the dnslookup router.

Voila! Exim *can* be configured to do what you want, without any
disliked nasties being put into the code.

If you email to a truly non-existent address, it will take 4 days before
you get a bounce. In my view, that is really bad, but if it's what you
want...


--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.