Subject: Re: [ietf-smtp] SMTP Over TLS on Port 26 - Implicit TLS Proposal
From: John C Klensin <[email-masked]>
To: Viruthagiri Thirumavalavan <[email-masked]>
Cc: [email-masked]
Date: Mon, 07 Jan 2019 07:41:16 -0500
List-Id: "Discussion of issues related to Simple Mail Transfer Protocol \(SMTP\) \[RFC 821, RFC 2821, RFC 5321\]" <ietf-smtp.ietf.org>

--On Monday, January 7, 2019 15:53 +0530 Viruthagiri
Thirumavalavan <[email-masked]> wrote:

> Trillions of mails sent every year. Why do we have to waste
> trillion of requests every year in trying for 465 when the
> signalling step can be embedded in the mx host name?
> 
> Can you give me a good reason, not to go for my solution?

Borrowing a bit from the note I sent a few minutes ago (please
read it first), there are efforts all around the world to get
DNS names into local writing systems and compatible with the
writing systems used in local languages -- so-called
"internationalized domain names" or "IDNs"   That effort has
already turned things like 
  www.<label-in-non-latin-script>.<label-in-non-latin-script>
into an ugly mess and invitation to assorted attacks, especially
if that script either looks a lot like Latin or is mostly
written right to left.   Naming conventions have their place and
can be really convenient, but turning them into protocol
elements rather than hints for convenience is just a really bad
idea.

If DNS tricks are needed and useful, use SRV records.

    john