I support this document going forward. Below I suggest four improvements to
the document.
(1) In Introduction says:
Note that this document doesn't apply to use of TLS in MTA-to-MTA
SMTP.
Can this be enhanced to include a pointer to where this can be found?
(2) The next paragraph in the Introduction says:
The main goal of the document is to provide consistent TLS server
identity verification procedure across multiple email related
protocols.
Since this is a standards-track document, I think it would be better to say:
This document provides a consistent TLS server identity
verification procedure across multiple email related protocols.
(3) Section 2 does a lot by reference, which is fine. I think it would help
the reader to duplicate a bit of context from RFC 6125, in particular repeating
the definitions of CN-ID, DNS-ID, and SRV-ID.
(4) Section 3 needs to state first that the certificate passes certification
path validation as described in Section 6 of RFC 5280, and second passes the
email-specific rules in this section.
Russ