[Emailcore] Ticket #13: G.7.7. Does the 'first digit only' and/or non-listed reply code text need clarification?

[Alexey Melnikov <[e-mail]>]

Hi,
I've changed the subject to reflect the correct ticket number. Commenting on the substance below.

On Thu, Dec 17, 2020, at 1:54 PM, Alessandro Vesely wrote:
> On Thu 17/Dec/2020 05:46:29 +0100 John C Klensin wrote:
> > --On Wednesday, December 16, 2020 22:41 -0500 John Levine wrote:
> >> In article <6A1255A557C666DF96E19DB9@PSB> you write:
> >>>	"It should use information in the other digits of the
> >>>	code and any supplemental codes or information (see RFC
> >>>	3463) only if it recognizes them and to provide
> >>>	additional information as needed but should rely on that
> >>>	first digit if the additional information is not
> >>>	recognized."
> >> 
> >> That seems utterly obvious, which I suppose means we should be
> >> sure to include it.
> > 
> > The discussion did come up on the mailing list and it is
> > possible --although I admit it is a stretch-- to read "Whenever
> > possible, a sender-SMTP SHOULD test the first digit (severity
> > indication) of a reply code it receives" as meaning "sometimes
> > it should not test even that" or leaving questions about what to
> > do with the test open.
> 
> 
> Yeah, especially when comparing that SHOULD with the fact that the first digit 
> MUST be checked if the response code is not recognized.  As if it were more 
> difficult to check the first digit than the whole response code.  Perhaps, 
> reading is easier if "Whenever possible" is replaced by something like "If the 
> sender-SMTP does not know how to deal with a specific response code".
> 
> Actually, only some response codes are better understood in their entirety, 
> e.g. 421.  The rest are for logging and offline pondering.

I tend to agree. How about the following strawman proposal:

OLD:
  Whenever possible, a sender-SMTP SHOULD test the first digit (severity indication)
  of a reply code it receives.

NEW:
  Sender-SMTP tests the whole 3 digit reply code it receives and any supplemental
  codes or information (see RFC 3463 and RFC 5248) if it recognizes them.
  Sender-SMTP MUST use the first digit (severity indication) of a reply code
  it receives if the full reply code or additional information is not recognized.

?

(Can additionally change "Sender-SMTP tests" to "Sender-SMTP SHOULD test" in the first replacement sentence)

Best Regards,
Alexey