Re: [ietf-smtp] How to encrypt SMTP?

[Дилян Палаузов <[e-mail]>]

Hello Keith,

On Sat, 2019-10-26 at 18:28 -0400, Keith Moore wrote:
> Yes but IMO we should be moving toward a world in which TLS is mandatory for SMTP relay.    Clear guidance to implementors and operators on what TLS versions, cert algorithms, and ciphersuites a client and server should support, might help us get there.
> 
> (perhaps as a stepping stone, cleartext mail relay could be pessimized by having servers randomly return 4xx in response to MAIL sent without TLS, obsolete TLS, or weak ciphersuites, with the probability of such responses increasing over time.)
> 

There is no big difference in the penalty between randomly returning 4xx on MAIL and randomly returning 4xx on RCPT and
the latter is effectively mail segmentation.

If random 4xx on MAIL as penalty for not offering reasonable TLS will help make things better, will random mail
segmentation as penalty for senders not supporting PRDR, convince anybody to implement PRDR?

Greetings
  Дилян