draft-macdonald-antispam-registry and interop

Hi all,

For those concerned about this draft and interoperability, could I get
further clarification?

1) Is it MTA to MTA interoperability?
2) If it isn't #1, what interoperability is it then?
3) if it is #1, could someone point out to me where is says that
extended SMTP error codes will impact MTA behaviour?

TIA

-- 
Jeff Macdonald
Ayer, MA