Re: [apps-discuss] Comments on draft-ietf-appsawg-greylisting-03

[SM <[e-mail]>]

Hi Murray,
At 15:41 16-02-2012, Murray S. Kucherawy wrote:
>So we agree that if one doesn't go for 421, then 450 is 
>appropriate.  But a server could say either one without any comment 
>text and be equally un-useful to the client.

Yes, to the "returns a 421 SMTP reply" in Section 2.1 as I do not see 
any other alternative.  For the rest, it would be 450.

>That is, if a client does 421 and dumps the connection, versus doing 
>450 but keeping the connection open (but probably unable to do 
>anything), I don't see the benefit of the latter for either 
>party.  Are you presuming that the 421 comment will be generic while 
>a 450 might be descriptive?

If the SMTP server sends a 421, it would force the connection to 
close.  The usual implementations usually provide some text with the 
450.  The 421 comment I have seen was generic.

I'll presume that a 421 means "service unavailable" as described in 
RFC 5321.  BTW, 421 is sometimes used for load shedding.

>The definition of AS from RFC2026 is:
>
>    An Applicability Statement specifies how, and under what
>    circumstances, one or more TSs may be applied to support a particular
>    Internet capability.
>
>I would say abuse mitigation qualifies as a "capability".

Local policy in SMTP provides leeway.  It can be used for abuse 
mitigation.  In my opnion, that's not an Internet capability.

Regards,
-sm