When i= domain != d= domain

,---
| d= The domain of the signing entity (plain-text; REQUIRED).  This
|    is the domain that will be queried for the public key.  This
|    domain MUST be the same as or a parent domain of the "i=" tag
|    (the signing identity, as described below).  When presented with
|    a signature that does not meet this requirement, verifiers MUST
|    either ignore the signature or reject the message.
'___

: d= The domain of the signing entity (plain-text; REQUIRED).  This
:    is the domain that will be queried for the public key.  This
:    domain MUST be the same as or a parent domain of the "i=" tag
:    (the signing identity, as described below).  When presented with
:    a signature that does not meet this requirement, verifiers MUST
:    consider the signature invalid.


Rather than suggesting the remedy of ignoring or rejecting the  
message, the signature should be defined as invalid.  Perhaps this  
represents some future version of the DKIM protocol, where a backward  
compatible signature may also be present.  It seems defining the  
state of the signature rather than possible remedies would be more  
useful.

-Doug