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DATA, 221, and close (was: Re: RFC2821bis-01 Issue 8 number of message transactions per connection ?)

2007-03-29 08:59:36

--On Thursday, 29 March, 2007 08:29 -0700 Bart Schaefer
<barton(_dot_)schaefer(_at_)gmail(_dot_)com> wrote:

On 3/29/07, Tony Hansen <tony(_at_)att(_dot_)com> wrote:

<implementor's hat>

  Side note: An implementation is free to respond with 4xx
  (e.g., 421, 451 or 452) to the MAIL FROM whenever it wants
to shut down the connection. And some implementations *do*
choose to do so because of local policy decisions.

</implementor's hat>

Recently I've encountered servers that respond with 221 rather
250 at the end of the DATA phase (after <CRLF>.<CRLF>) and then
immediately close the connection.  (This may not be a
recently-developed practice, but I noticed it for the first
time last
week in an SMTP client log when tracking down a delivery

There is at least one well-known server that behaves in this
general way (perhaps not this specifically).  It is generally
believed to be non-comformant in many other ways as well.

It would appear this is meant as an indication that the server
to accept exactly one message and doesn't care to wait for a

The developer of that server has argued that he should not need
to wait for a QUIT and that, when the same software is operating
as a client, he should, at most, send a QUIT and then close
without waiting for a response.
I'm not sure what, if anything, could be put into the document
this.  Perhaps guidance as to how clients should react when
the server
wanders off-protocol?  In the case I was investigating the
treated the situation as a 4yz and retried the message later,
to a lot of copies being delivered and (fortunately just one)
irate recipient.

That would strike me as client behavior within the intent of the
protocol.  And, no, I don't have any idea how to write up
suggestions about how clients should deal with misbehaving /
non-conforming servers without getting into a rather large
rathole.  I think there might well be a place for an "SMTP
operations in  the face of stress, stupidity, well-intentioned
by out-of-spec spam solutions, and deliberate misbehavior", but
I don't think it should be part of 2821bis.

(I've also seen 221-and-close responses to EHLO, which seems
entirely bizarre.)

yeah.  Presumably, it would mean "I'm closing now, but I thought
your EHLO command was ok, so keep trying".  And I can't imagine
why one would want to deliver that message.

I have not assigned an issue number to this one.  If someone
wants to state it as an issue or request for action, please do


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