Re: [Asrg] What are the IPs that sends mail for a domain?

Ian Eiloart <iane@sussex.ac.uk> Wed, 17 June 2009 10:49 UTC

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Subject: Re: [Asrg] What are the IPs that sends mail for a domain?
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--On 16 June 2009 19:17:41 -0400 Daniel Feenberg <feenberg@nber.org> wrote:

>
> I predict that no significant amount of mail ever originates from IPV6.
> Because it would be impossible to maintain a DNSBL for IPV6, I expect
> that enough sites will decline all IPV6 mail that it won't pay to send
> from it.
> Consider that because a spammer could (spoof) a different IPV6 address
> for every message, even a different 48 bit block for every messages, MTAs
> will be left with only content analysis for spam blocking.

Which is why reputation services need to be based on sender domains, not IP 
addresses. Users can then whitelist as required, and use of IP 
addresses/domains without good positive reputation won't work very well.

The advantage of IPV6, of course, is that you'll never have to share an IP 
address with someone with poor reputation.

> I don't expect
> IPV4s will ever be so scarce that enough MTAs will start using them out
> of necessity - ISPs will give each customer 4 IPV4 addresses with their
> million address IPV6 range, and customers will use those 4 addresses for
> the things that really need IPV4 - such as internet facing MTAs.



-- 
Ian Eiloart
IT Services, University of Sussex
01273-873148 x3148
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