[ietf-dkim] Attempted text for x=

[Jon Callas]

On 19 Apr 2006, at 10:14 AM, Paul Hoffman wrote:

> What is the interoperability or harm-limiting purpose of verifiers  
> checking x= values? If there is none, the sentence above needs to  
> be a MAY.

I don't want to torture people with my reasoning, but x= needs to be  
a MAY, but for possibly different reasons.

My reasons are that I don't think that an implementer needs to  
"carefully weigh" whether to implement x=. I think that casually  
weighing it is just fine. I've been thinking a lot about uses for x=,  
and some of them might allow someone to game DKIM against other parts  
of a mail filtering system. And yes, I know that this comes close to  
conflating SHOULD-implement vs. SHOULD-deploy, but I would not think  
ill of an implementor whose decision was "I don't understand it well,  
so I'm not implementing it," which is the antithesis of SHOULD.

	Jon