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Re: draft-klensin-rfc2821bis-04: VRFY and EXPN syntax

2007-07-15 10:40:20
On 2007-07-14 23:50:25 -0700, SM wrote:

At 17:09 14-07-2007, Peter J. Holzer wrote:
Yes. When I did some experiments with SMTP callbacks some time ago, I
found that most MTAs return that (I wonder what advertising the VRFY
capability in the EHLO response and then returning a useless result is
supposed to accomplish ...), but even worse, some expected the email
address in angle brackets and some without, so you would get false
negatives unless you tried both ... Too much trouble for too little

It might be better to list VRFY in the EHLO response only if the 
command is supported by the installation.  The "if EXPN is supported, 
it MUST be listed as a service extension in an EHLO response." would 
still apply.

Draft-04 does not specify that angle brackets must be used.


The example in that section could be clearer if it was:

      C: VRFY smith
      S: 553 User ambiguous


      C: VRFY smith
      S: 553- Ambiguous; Possibilities are
      S: 553-Joe Smith <smith(_at_)example(_dot_)com>
      S: 553-Harry Smith <smith(_at_)example(_dot_)net>
      C: 553 Melvin Smith <smith(_at_)example(_dot_)org>


      C: VRFY smith
      S: 553-Ambiguous; Possibilities
      S: 553- <jsmith(_at_)example(_dot_)com>
      S: 553- <hsmith(_at_)example(_dot_)com>
      S: 553 <dweep(_at_)example(_dot_)com>


       C: VRFY <smith(_at_)example(_dot_)com>
       S: 250 smith <smith(_at_)example(_dot_)com>


       C: VRFY smith(_at_)example(_dot_)com
       S: 250 smith <smith(_at_)specific(_dot_)example(_dot_)com>

The last two would be a separate example, I think. 

The before last example is for a user name and domain.  Although it 
is accepted by some implementations, and I believe, readily used, it 
does not fit the description for a string as a user name.

It falls under 'hosts MAY also choose to recognize other strings as
"user names"'. The last form is IMHO the only form which must be

|  An implementation of the VRFY or EXPN commands MUST include at least
|  recognition of local mailboxes as "user names".  However, since
|  current Internet practice often results in a single host handling
|  mail for multiple domains, hosts, especially hosts that provide this
|  functionality, SHOULD accept the "local-part(_at_)domain" form as a "user
|  name";

So "local maiboxes" MUST be supported ans "local-part(_at_)domain" SHOULD be
supported. But how is a mailbox specified? 

|  The standard mailbox naming convention is defined to be
|  "local-part(_at_)domain":

Seems a bit redundant to prescribe the same form both via MUST and


   _  | Peter J. Holzer    | I know I'd be respectful of a pirate 
|_|_) | Sysadmin WSR       | with an emu on his shoulder.
| |   | hjp(_at_)hjp(_dot_)at         |
__/   | |    -- Sam in "Freefall"

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