BTW - I now support that both TXT and SPF RR records be done
in SRV way:
_smtp._tcp.example.com. IN TXT "SPF2.0/PRA ..."
_smtp._tcp.example.com. IN SPF "SPF2.0/PRA ..."
I would support this as well.
What we have here is a set of policy extensions that are bound
to ONE protocol. Over time all protocols are going to require
a similar mechanism to allow them to advertise their security
policy.
If we define the special case we will inevitably end up defining
the general case in due course, sure as SRV followed MX.
Phill