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List:       exim-users
Subject:    Re: [Exim] Exim 3.02 smtp session hangs (name/ip resolv problems?)
From:       Philip Hazel <ph10 () cus ! cam ! ac ! uk>
Date:       1999-07-27 8:39:42
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On 25 Jul 1999, Ulrich Schwarz wrote:

> IP address lookup yielded fruli.ddns.org
> Alias mail.fruli.ddns.org
> Alias news.fruli.ddns.org
> Alias www.fruli.ddns.org
> Alias localhost
> ************************************************************************
> **** the SMTP session hangs at this point for several (5-10) minutes ***
> ************************************************************************
> Actual local interface address is 127.0.0.1
> Actual local interface address is 62.157.19.26

Once Exim has looked up the host name(s) from its IP address, it then does 
a lookup of the name(s) that it got, in order to check that they match. 
Otherwise, any old IP address could be made to point to the wrong name 
by somebody wanting to cause trouble. This doublecheck was introduced at 
release 2.03.

It would seem that it is this forward DNS lookup that is going slow.
Exim just calls gethostbyname() to do it.


-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@cus.cam.ac.uk      Cambridge, England. Phone: +44 1223 334714.

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