[ietf-dkim] RFC4871bis - whether to drop -- l= and x=

[Murray S. Kucherawy]

> DKIM is not limited to just email.   Even ADSP failed to limit its
> assertions to just email.  As such, what should unspecified message
> formats contain?

One would think the "unspecified message formats" would have defining documents someplace that identify header fields that are supposed to be present to be compliant.  So the generic language John suggested seems fine to me.