On Fri, 7 May 1999, Marilyn Davis wrote:
> But this from Peter Lister worries me:
>
> > If I understand you correctly, you wish to check IP
> > addresses (i.e. the 32 bit number not the domain name) - I take it you
> > know that there is frequently very little relation between the two.
> Can you explain how it legitimately happens that IP addresses and
> domain names aren't related?
I'm not entirely sure what you are asking or what Pete said (I didn't see
his message).
First there is a shocking number of hosts sending mail without proper
reverse (PTR) lookups. So there are legitimate, but misconfigured,
mailhubs for which you can't map from IP address to any domain name.
Secondly, it must be noted that addresses and names constitute a many to
many relationship. A single name can have multiple IP addresses:
% nslookup www.pgp.net
Name: www.pgp.net
Addresses: 128.232.0.23, 129.242.4.248, 129.142.64.11, 131.234.116.2
129.132.119.131, 209.151.24.2, 195.64.0.35
And a single IP address can be associated with a large number of names.
Also a single host can have serveral IP addresses (often WWW virtual
hosting is done that way).
But I am not sure if PRL is referring to other sorts of things.
> > ObExim: should exim really worry about this? IMO it ought to leave blocking
> > source routed stuff to the OS and/or network infrastructure.
>
> I'd say yes. Exim should worry about it.
I agree. In principle, of course, these should be handled at by the OS
and/or the networking boxes. But it is useful to have this also
configurable for particular services.
-j
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