Re: SMTP Over TLS on Port 26 - Implicit TLS Proposal [Feedback Request]

["Constantine A. Murenin" <mureninc () gmail com>]

On Fri, 11 Jan 2019 at 22:00, Suresh Ramasubramanian
<ops.lists () gmail com> wrote:
> Most new MTA implementations over the past several years default to TLS with strong ciphers.  So how much of a 
> problem is low or no TLS right now?

The real problem is that opportunistic StartTLS stops being
opportunistic the minute you encounter a `STARTTLS` extension on
`EHLO`.

At that point and henceforth, TLS is pretty much 100% mandatory.

What happens if there are SSL negotiation failures?  I'll tell you
what happens — the sender will receive a few bounces, X hours and Y
days after sending the mail; recipient doesn't receive anything at
all.  (Unless, of course, one of the administrators would magically
decide to change the SSL options in the meantime to be compatible, or
to disable the "opportunistic" StartTLS to start with, before the
final bounce gets generated by the MTA of the sender.)

These problems are real.  They're already happening today.  StartTLS
being "opportunistic" is a pretty big scam.

C.