In <20040224165948(_dot_)GZ27676(_at_)dumbo(_dot_)pobox(_dot_)com> Meng Weng 
Wong <mengwong(_at_)dumbo(_dot_)pobox(_dot_)com> writes:
Let's find a way to express the desired new functionality in the
existing syntax.
perhaps scope=mailfrom,helo?
On a somewhat related subject, it would be nice if you could mark SPF
records as being valid for include: mechanisms only.  It is awfully
tempting to use something like include:%{l}.spf.%{d}, and have that
resolve to "v=spf1 +all" in some cases.  However, that opens up those
subdomains for being abused.
-wayne