I am the assigned DNSDIR reviewer for this draft. I am knowledgeable in the area of email, SMTP and crypto in general and I do understand the issues being discussed. I do not, however, consider myself an expert on the topics covered in this document.

This document does not contain any references to DNS other than in the sections for Future Work and several references. As such there is nothing much DNS-related for me to review.

That said, I like this document and the effort that has been put into it, in particular given its length. It is very well structured which is much appreciated. 

I expected to have more things to say about structure but in the end I only have one minor nit in that area: I think it would be easier if you listed at least the referenced RFCs in numerical order (split into normative and informative, as needed).

Johan Stenstam