At 8:48 PM -0500 2/11/05, Bruce Lilly wrote:
> Date: 2005-02-10 19:09From: Randall Gellens <randy@xxxxxxxxxxxx>
At 3:03 PM -0500 2/10/05, Bruce Lilly wrote:
> There are some differences between what the draft says and that > description: > 1. the draft explicitly permits operation on port 25 > 2. the draft section 4.3 doesn't mention port. > > Specifically regarding the 4.3 MUST quoted above and the reply code, > and the necessary two independent implementations required for > advancement to Draft Standard status, do the implementations supporting > the request to advance to Draft in fact unconditionally require > authorization (i.e. independent of whether port 25 or 587 is used, and > regardless of administrative configuration other than specifying that the > implementation is to act as an MSA), and reply with code 530 (unspecified > extended response code) if authorization is lacking?
Both the draft and RFC 2476 allow submission to use 25 instead of 587, but state that "normally" 587 is used, and allow 25 to be used in order to accommodate implementations that are hard to configure. Both say that port 587 is reserved for submission. So, 587 is the normal case for submission, and 25 is an exceptional case.
But as written, section 4.3 specifies that when acting as an MSA, authentication MUST (emphasis in original) be used, regardless of port.
Section 4.3 says "unless it has already independently established authentication or authorization (such as being within a protected subnetwork)." It's not uncommon for organizations to deploy MSAs that treat all internal connections as authenticated, even if they allow travellers to connect in using port 587 and in that case require authentication.
> Please see the implementation report for the details, but I believemost implementations had various configuration options that allowed them to require authentication or not.
Again, "or not" is not allowed by the draft as written; implementations with an "or not" provision would fail to comply with the "MUST" (they would comply with a "SHOULD", however).
My understanding is that implementations are permitted to have configuration options that allow sites to deploy them in ways that violate the RFCs, as long as they can be operated in a conforming manner. For example, it is not uncommon for POP implementations to have options to have timeouts shorter than mandated, or to enter UPDATE state on abort.
There are several implementations which have default configurations which do comply with 4.3, even if they have non-default configurations which do not comply. Likewise, there are other implementations which have a default configuration which does not comply, but can be configured to comply.
Aside: based on my understanding of the implementation report, there are no two implementations which simultaneously comply with all of the draft (or 2476) provisions, failing the "two independent implementations" test for advancement to Draft Standard status.
From my understanding of the requirements, thereare multiple implementations which comply. This is based on two points: (1) implementations can be compliant even if they have options which permit non-conformance; and (2) there must be at least two implementations for each feature, but it is not required that any individual implementation meet every SHOULD. I believe Message Submission meets the criteria on the basis of either of these points; the fact that it meets it on both is nice but not required.
> > prohibited" [RFC 3463 section 3.7]. The corresponding RFC 3463> On another matter, admittedly unchanged since RFC 2476, there seem to > be some undesirable discrepancies between submission and non-submission > ESMTP regarding extended response codes. Draft section 3.4 states that > extended status code 5.6.2 means "Bad domain or address", whereas > RFC 3463 assigns that code the semantics "Conversion required and> extended response code for domain/address issues would be in the
> 5.1.XXX range [RFC 3463 section 3.2]. The draft specifies (sect. 5.1) use
> of 5.6.2 with 554 for message header field address issues when an error
> is reported after DATA. SMTP (RFC 2821) does not require examination
> of message header address field content except in the particular case
> of a gateway [RFC 2821 section 3.8]. If the intent is that MSAs are
> always to be considered to be gateways, then the draft should explicitly
> say so (the term "gateway" does not appear anywhere in the draft).
> [that would be a novel use of the term "gateway" in Internet mail; a
> gateway usually has one side in a non-SMTP environment]
> Conversely, if MSAs are not always to be considered as gateways, then
> returning errors in response to message content is:
> 1. explicitly counter to the SHOULD NOT of RFC 2821 section 3.4 (bottom of
> page 18)
> 2. inappropriately associated with "conversion" semantics where no
> conversion is in fact required (indeed, other than adding trace fields,
> tinkering with message data by non-gateway SMTP receivers is disallowed
> [RFC 2821 section 2.3.8]).
It is not the intent of either this draft or RFC 2476 to say that MSAs are always gateways; rather, the intent in both is to recognize the reality that organizations sometimes see a need to examine and potentially modify messages submitted using their servers, and to make a clear distinction between this case, and the examination/modification of messages being relayed.
Well, there's an unresolved incompatibility with RFC 2821.
Following up on a disturbing sense of déja vu, I checked my records and found the following commentary on RFC 2476 -- I believe that the issues remain largely unaddressed by the draft: --------------------- Date: Sat, 17 Apr 2004 22:54:44 -0400 From: Bruce Lilly <blilly@xxxxxxxxx> Reply-To: blilly@xxxxxxxxx Organization: Bruce Lilly User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7b) Gecko/20040316 X-Accept-Language: en-us MIME-Version: 1.0 To: John C Klensin <klensin@xxxxxxx>, Randy@xxxxxxxxxxxx Subject: Comments on RFC 2476 (Submission protocol) X-Enigmail-Version: 0.83.5.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-UID: 407 X-Length: 3072
Hello,
First, the reason that I'm sending this directly rather than to ietf-submit is that
I'm not subscribed to that list and in a few hours I'll be on an airplane on a
business trip, and I may be incommunicado for a week or so. By all means feel free
to forward my comments to the list and/or to Chris Newman (whom I see has made some
list contributions about a month ago; unfortunately the list archive on the IMC web
sit only displays "Chris Newman <Chris.Newman@xxxxxxx>" and the corresponding
mailto link is the useless "mailto:Chris.Newman@xxxxxxxxxxxxx";).
Following are my comments, in the order as presented in the RFC:
section 3.2, last NOTE:
Of course the MSA, in order to "properly handle delayed bounces" will have to be
able to accurately determine the source, which s probably only possible is some
authentication mechanism is used.
section 3.4 enhanced status codes:
This is the biggest problem that I see: the basis is RFC 1893 (superseded by RFC
3463) status codes, which specifically address only issues related to hard errors
in delivery. For example, there is no standardized extended status code to address
the situation where an email address is not valid but a forwarding address is
available. 3463 does address the situation where such a forwarding address is NOT
available (5.1.6), but not the situation corresponding to SMTP response 251.
2.1.6 might be an appropriate extended status code, but RFC 3463 specifically
states that X.1.6 " is only useful for permanent failures", i.e. 5.1.6.
One might hope that some unified set of extended status codes might be developed
that could be used for multiple protocols. Unfortunately, there seems to be an
inconsistency even within the mail protocols. RFC 2476 lists extended status code
5.6.2 as "Bad domain or address", whereas RFC 3463 (and 1893) list that code as
"Conversion required and prohibited". That is very confusing, since RFC 3463
provides a range of extended codes (x.1.0 through x.1.8) for address/domain
errors.
It is also notable that RFC 2476 (e.g. section 4.1) provides no extended status
codes for transient failures or for success; only class 5 -- permanent failure.
Another example of the extended status issue shows up in RFC 2476 section 5.1,
which again addresses only permanent failures, not temporary failures (e.g.
DNS transient failures). It also doesn't distinguish between syntax errors
and address semantic errors.
Best regards, Bruce Lilly ----------------------------------
There does seem to be a disconnect between the meaning of 5.6.2 in the Message Submission documents and the Extended Status Codes documents, and this should be fixed in this revision, perhaps by deleting specific extended response codes from this revision, at least those that overlap or conflict with those already specified elsewhere.
--
Randall Gellens
Opinions are personal; facts are suspect; I speak for myself only
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All generalizations are false, including this one.
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