RE: SMTP filtering use case

It's very difficult to satisfy the IAB concerns by saying that callout
servers will handle all policy - we aren't specifying the callout
server applications.  

I think that scenarios which can be satisfied by a switch are just
fine, but if they can be deployed today without any new protocols,
then they aren't topics for discussion in this WG, except as negative
examples, i.e., "you don't need OPES for that".

Hilarie