spf-discuss
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Re: Validator Testing Request

2005-08-08 23:27:31
On Aug 8, 2005, at 10:17 PM, wayne wrote:
However, the ptr *does* count.  This ptr lookup is not the same as the
one in 1) because it refers to easydns.com, not cox.net.  Even if it
was the same, they would both count.

Thanks for the explanation Wayme, however that strikes me as strange. As I understand the spec the number of mechanisms and modifiers that do DNS lookups is limited to 10. But surely, since any ptr mechanism after the first doesn't need to invoke an additional PTR lookup, shouldn't they not count against the limit? Multiple ptr mechanisms in a single SPF record presumably just cause SPF to add the specified domains to the list of acceptable parent domains for a single PTR lookup performed on the server IP address (since this IP address doesn't change over the course of the SPF record evaluation). In the case of my example, the DNS PTR lookup at step 2 should be sufficient for all ptr mechanisms. Am I misunderstanding something? Is an SPF implementation expected to issues multiple identical DNS PTR lookups on the server IP address if there are multiple ptr mechanisms?

-Richard