Checking all identities or letting people choose (Was: moving on from MA

On Fri, Sep 24, 2004 at 12:52:07PM -0400,
 Meng Weng Wong <mengwong(_at_)dumbo(_dot_)pobox(_dot_)com> wrote 
 a message of 71 lines which said:

> Unified SPF, with the following main points:
 
> 1) Receivers should check all three identities:
All? It seems technically strange (you may allow different servers for
2821 Mail From and for the PRA) and contradicts the Vixie principle of
"We do not know yet the proper identity to check, let's allow people
to check the one they want".