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

Alessandro Vesely <> Fri, 19 June 2009 10:54 UTC

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Subject: Re: [Asrg] What are the IPs that sends mail for a domain?
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John Levine wrote:
>>Isn't the FQDN for a host the host name "dot" the domain name?
> The FQDN for a host is the host's FQDN.  As we've all noted, there's
> lots of heuristics to guess domain names, none of which work.

What about the other way around: given a domain and an IP address, can 
we say whether the IP address "is a member of" the domain?

Vhlo mentions the following three ways to determine that, without 
apparently resorting to heuristics. I'm wondering how sound it is to 
rely on those, or similar, techniques.

* rDNS returns a name whose right part matches the domain name,
* an MX record for the domain mentions a host with the given IP,
* the IP address passes the SPF check for that domain.