>4.1.  Notes on handling of SRV-ID by Certification Authorities
>5.1.  Notes on hosting multiple domains

The multiple domain stuff still needs work, and there seems to be
confusion between the domain name of the server (CN or SRV-ID) and the
domain name(s) for the mail it handles (DNS-ID.)  In nearly every case
the server and the mail will have different domain names, usually with
no lexical connection, e.g. a zillion little hosted mail domains all
pick up their mail from imap.gmail.com.

The SNI discussion is wrong because SNI only affects CN or SRV-ID, and
anyway at the time the TLS connection is made, the client can tell the
server the name of the server it wants, e.g. imap.gmail.com, but not
the domain of the mail it's planning to pick up, since the first place
the mail domain is mentioned is the login which happens after the TLS
session is set up.

Separate domain names and SNI could work if there's a separate server
name per mail domain all pointing at the same server, e.g.
smallco.biz.imap.gmail.com, but that scales poorly, and there's still
no way for a CA to sign it since there's no way for a CA to tell what
mail domains go with which servers.  It's pretty ugly, too.

I suggest taking out most of the multiple domain stuff and say that there's
currently no automated way to match mail domain to server domain in other
than a few special cases, and it needs more standards work, like telling
people to use DNSSEC+RFC 6186.

R's,
John

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