Re: [Exim] Disable rDNS checking?

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Author: Philip Hazel
Date:  
To: jasonr
CC: exim-users
Subject: Re: [Exim] Disable rDNS checking?
On Thu, 21 Dec 2000 jasonr@??? wrote:

> Is it at all possible to disable *all* rdns lookups for smtp sending?


Do you really mean sending? I don't think Exim ever does reverse lookups
while sending.

Or perhaps you mean when something else is sending TO Exim?

Exim only looks up a host name if

(a) You tell it to, by setting host_lookup.

(b) It needs the name because you have specified some checking by name,
e.g. something like

host_accept_relay = *.some.domain

(c) The client host is broken, and sends a HELO command like

HELO the.server.domain.name

What it is supposed to send is

HELO the.client.domain.name

In this case Exim does a lookup to get a client name. Otherwise the
entries in the log get very confusing.

You can test why Exim is doing a lookup by running a simulated SMTP
session using the -bh option, e.g. exim -bh 1.2.3.4 This should
enable you to find out why it is doing lookups.

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