Richard Parker wrote:
that strikes me as strange.
Not really, if you have "v=spf1 a a a a a" it's five mechanisms
- we cannot expect implementations to "think" about such crap.
As soon as you'd try to "think" we'd be again in the deep shit
of "a:1.2.3.4 is the same as ip4:1.2.3.4. or ipv4:1.2.3.4",
and that turned out to be a bad idea last year, users are very
"innovative" with errors.
Normally it's "be tolerant in what you accept", but for SPF it
is very important that the same policy has the same effect with
all receivers (modulo TempErrors incl. DNS timeouts). OTOH if
it sometimes apparently works, sometimes fails, and sometimes
has unexpected effects, then SPF would be unreliable and dead.
Is an SPF implementation expected to issues multiple
identical DNS PTR lookups on the server IP address if
there are multiple ptr mechanisms?
Sure, it's in the DNS cache, no problem. It's the purpose of a
cache to accelerate identical queries. Instead of other tricks
like noting what you've done, because you don't want to do it
again for the same MAIL FROM. A cache is much smarter, it also
works for the next MAIL FROM.
Bye, Frank