MX dot RE: [ietf-dkim] TXT wildcards SSP issues

[Steve Atkins]

On Jun 2, 2007, at 8:21 PM, Hallam-Baker, Phillip wrote:

> Steve,
>
> Could you expand on this somewhat?
>
> We may be able to push the beastly wildcard issue into touch  
> altogether here.

I suspect not, but it's worth a try.

> What is the deployed base for MX . ?

I've no idea. I have a zone file and some survey code, but haven't  
pointed
it at that question yet - it may be time to take a look.

> How widely is it recognized?

Fairly widely, I suspect, by spam filters that look for a deliverable  
email
address in the envelope from. All "MX ." does is provide an invalid
MX record that's easily recognized as being intentional (similar to
the .invalid pseudo-TLD in many respects).

http://ietfreport.isoc.org/idref/draft-delany-nullmx/ is the  
(expired) draft
that formalizes the concept, and it was somewhere between discussed
and common knowledge for at least a couple of years before it was
drafted in '05.

> Used?

Not as widely as I thought, apparently. I'm not sure.

Cheers,
   Steve