> -----Original Message-----
> From: owner-postfix-us...@postfix.org 
> [mailto:owner-postfix-us...@postfix.org] On Behalf Of Larry Stone
> Sent: Friday, 12 December 2008 3:53 PM
> To: postfix-users@postfix.org
> Subject: Re: Postfix does not dot the i's when client sends gibberish
> 
> On 12/11/08 9:41 PM, Victor Duchovni at 
> victor.ducho...@morganstanley.com
> wrote:
> 
> > On Fri, Dec 12, 2008 at 12:59:41AM +0100, klondike wrote:
> > 
> >> According to section 4.2.4 on the RFC 282, the SMTP server should 
> >> return
> >> 502 only when a command is recognised but not implemented, 
> and 500 if 
> >> it isn't recognised.
> > 
> > This is not a bug, but it is admittedly an unecessary deviation from

> > SHOULD normative language in the RFC when the client is in flagrant 
> > violation by sending garbage.
> 
> At the risk of moving away from Postfix technical issues, RFC 
> 2821 is poorly written. SHOULD, despite much misuse in 
> commonly used English, is the past tense of SHALL. Something 
> that SHALL be done is mandatory yet in common but incorrect 
> use, SHOULD is often used to mean present tense MAY (as in 
> you can do so but it is not mandatory). As a formal document, 
> the RFC ought to say either SHALL (mandatory) or MAY 
> (optional) with SHOULD, being in the past tense, completely 
> incorrect in the context of that paragraph. Unfortunately, 
> given the incorrect use of SHOULD, it is unclear to me what 
> the RFC really means.
> 
> --
> Larry Stone
> lston...@stonejongleux.com
> http://www.stonejongleux.com/
> 

I don't know when it happened (I don't have the OED to hand), but for
quite some time (at least decades), "should" has not *solely* been the
past tense of "shall". As an _auxiliary_ verb, it has the following
accepted senses:

1. ought (to be or do something); Indicates that the subject of the
sentence has some obligation to execute the sentence predicate. 
You should go to the doctor if you have a severe fever. 
2. will likely (become or do something) Indicates that the subject of
the sentence is likely to execute the sentence predicate. 
You should be fine soon if he treats you with an anti-pyretic. 
3. If; in case of; Indicates that its subordinate clause refers to a
hypothetical condition for the event expressed by main clause. 
Should you need to contact the doctor right away, you will need to use
the after-hours number.

To insist you don't understand a common and accepted modern usage of
"should" is disingenous in the extreme. I do think "ought" is often
better in formal documentation, though. But as long as the use of a term
is clearly defined in a document - as it is in the RFCs - it actually
doesn't matter what might be "correct". Technical, scientific and
academic English can be quite different to Standard English.

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