Re: [ietf-smtp] IETF Policy on dogfood consumption or avoidance - SMTP v

On 2019-12-19 17:52:53 -0500, Hector Santos wrote:
> On 12/19/2019 1:32 PM, Viktor Dukhovni wrote:
> > This includes RBL checks, presence of PTR, PTR name regexp checks, ...
> > Rejecting address literal in EHLO is a filter in this class, that can
> > be justified entirely on its efficacy.  If the reported one complaint
> > in 10 years is about right, then it is working well enough in practice.
> I don't agree this is a justification to bring break a base SMTP protocol
> feature.
[...]

> The fact is, there is a SMTP protocol rule of using a HELO/EHLO [ip-literal]
> that MUST match the connection IP.  If not, it is a strong reason for
> rejection.  I have wcSAP stats for that.
You are aware that you are directly violating a MUST NOT constraint in
the RFC by doing this, while there is no such constraint against
rejecting all IP literals (or just IP addresses equal to 7 modulo 13,
FWIW). I don't think you can argue with protocol compliance on this.


> The difference with the SDO is a flat rejection of ip-literal based on some
> subjective notion that ALL senders using ip literals are bad.
>
> If it rejected on the rDNS detection that a FQDN was available and enforces
> its usage, that may be a easier argument to sell because it is a
> deterministic rule.
I am very unclear on what you understand to be "deterministic". 

You seem to be making assumptions on what a "good operator" should do,
use statistics to verify that applying these assumptions as rules have a
sufficiently high true positive and false negative rate and then call
them "deterministic".

If other people do the same (but with assumptions that don't match
yours) you call it "subjective".


> By far, CBV is the highest payoff filter right now, today,
> bar none, than any other known method.
There are some people (not me) who consider CBV abuse.

        hp

-- 
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp(_at_)hjp(_dot_)at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"

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