Re: [exim] Add a header when reverse DNS fails or defers?

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Autor: Philip Hazel
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A: Marc Sherman
CC: exim-users
Assumpte: Re: [exim] Add a header when reverse DNS fails or defers?
On Fri, 21 Jan 2005, Marc Sherman wrote:

> Hrm. If seems that a defer doesn't set host_lookup_failed to 1 (at least in
> exim 4.34).


Indeed. host_lookup_failed is badly documented. I will improve the
description for the next release. What a value of '1' means is "I tried
to look up a host name, and there wasn't one". That's why somebody
invented some clever ACL-ery to distinguish between

. Found a host name
. Found there was no host name
. Dunno - dns lookup problems

Note that the last one does not mean there is an intrinsic problem with
the host or its DNS data. It just might be that somebody dug through the
cable leading to its nameserver. (Well, that is a problem if it doesn't
have another nameserver, but you get the idea.)

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book