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Re: When MX is not present, fall back to A

2003-12-14 14:58:33


--Meng Weng Wong <mengwong(_at_)dumbo(_dot_)pobox(_dot_)com> wrote:
Now, in the draft's definition of "mx", we can either continue the
broken tradition, or set a new standard.
[...]

Breaking with tradition:

   If the <target-name> has no MX records, SPF clients MUST NOT pretend
   the target is its single MX, and MUST NOT default to an A lookup on
   the <target-name> directly.  If such behaviour was intended, the
   <target-name> would have specified an "a" declaration instead.


I would totally agree with this. You might insert a sentence to clarify like "Specifying "mx" in the SPF record when there are no MX records for the domain should have no effect."

If someone has a domain with A record and no MX, and wants to receive mail, they should be encouraged to define MX records. Most A records within the domain define servers or web sites that are not used for email. It looks like there is no real alternative to specifying SPF records for each A record, but I can't see an easy way around that. Probably most admins won't do this until someone actually forges one of the names, but I'm afraid this will become more common as the top-level domains get protected.

Perhaps over time people will start refusing mail for domains that have no MX and the grandfather clause will be useless and done with. But this will take time... Meng's suggestion here is a good balance between forward-looking and not-too-far-reaching, IMO.

gregc
--
Greg Connor <gconnor(_at_)nekodojo(_dot_)org>

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