Putting on my area director hat:
An RFC 3207 STARTTLS revision needs text related to server identity check.
I would prefer this text be as similar as possible to server identity check
text in other IETF application protocols.
For Submit, I'd expect the TLS server identity check to be
mandatory-to-implement and very close to that of IMAP and POP (or to have a
justification why it shouldn't follow IETF practices for this).
I've attempted to get volunteers to write a generalized TLS server identity
check for use by applications so it can be included by reference. The
initial draft has unfortunately expired:
<http://tools.ietf.org/html/draft-hodges-server-ident-check-00>
and needs work. This issue has come up in _many_ WGs and protocols.
For SMTP transfer, the situation is different and probably needs technical
discussion to reach consensus on the path forward. It would not surprise
me if we needed one or more additional EHLO keywords/arguments to resolve
legitimate concerns. I will observe that for SMTP without SMTP AUTH, there
is value in opportunistic STARTTLS encryption without authentication as
long as the risks are understood.
- Chris