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Re: [ietf-dkim] lets add one more shall we?

2007-06-06 15:27:29
Douglas Otis wrote:

To that end:

Obsoleting the A record discovery process will establish one location for _any_ email related policy record, and not just that for DKIM.

If I understand you, this isn't working to work Doug. A records are required.

Are you familiar with the MX lookup and expansion process?

In case you didn't, the MX query does not always result in IP addresses. The IP addresses are obtained in A lookups of the host names by provided by the MX records.

In other words, not all MX query gives you IP addresses to try.

A good example is YAHOO.COM:

C:\> nslookup -query=A yahoo.com

Non-authoritative answer:
yahoo.com       MX preference = 1, mail exchanger = f.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = g.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = a.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = b.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = c.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = d.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = e.mx.mail.yahoo.com

Now you expand each of these:

C:\> nslookup -query=A f.mx.mail.yahoo.com

Non-authoritative answer:
Name:    f.mx.mail.yahoo.com
Addresses:  209.191.88.247, 68.142.202.247

and you do this for EACH the MX host records to finally get a total expanded list of IP addresses.

--
Sincerely

Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com

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