need organizational hint

[Phil Howard]

On Fri, Apr 11, 2003 at 01:29:21PM +0100, Ian G Batten wrote:

| On Thu, 10 Apr 2003, Adam Tauno Williams wrote:
| > > 4.  Delivery attempts to a non-existant user must always give a
| > >     550 error response.  No queueing of a any delivery failure
| > >     messages whatsoever.
| > 
| > This is the default behaviour of MTA->Cyrus (via LMTP) delivery.
| 
| Are you sure?  Sendmail 8.12.9 with the cyrusv2 backend, Cyrus 2.1.12:
| 
| 220 offsite.batten.eu.org ESMTP (No Unsolicited Commercial Email)
| ehlo localhost
| 250-offsite.batten.eu.org Hello localhost.localdomain [127.0.0.1], pleased to meet you
| 250-[...]
| 250 HELP
| mail from:<igb at batten.eu.org>
| 250 2.1.0 <igb at batten.eu.org>... Sender ok
| rcpt to:<this.name.does.not.exist.honestly at batten.eu.org>
| 250 2.1.5 <this.name.does.not.exist.honestly at batten.eu.org>... Recipient ok
| data
| 354 Enter mail, end with "." on a line by itself
| From: igb
| To: rubbish
| Subject: hello
| 
| 
| 1234
| .
| 250 2.0.0 h3BCR10d019664 Message accepted for delivery
| 
| I then get mailed back:
| 
| [...]
|    ----- Transcript of session follows -----
| ... while talking to [127.0.0.1]:
| >>> DATA
| <<< 550-Mailbox unknown.  Either there is no mailbox associated with this
| <<< 550-name or you do not have authorization to see it.
| <<< 550 5.1.1 User unknown
| 550 5.1.1 <this.name.does.not.exist.honestly at batten.eu.org>... User unknown
| <<< 503 5.5.1 No recipients
| 
| ian

Maybe he was referring just to Postfix, since I had mentioned it being the one
I would use.  Conceivably, the MTA could open the LMTP session while the SMTP
session is still active.  I would guess it would have to at least wait until it
gets RCPT TO in order to do that since different recipients could have different
delivery destinations that would not all be on the same mail system, such as by
different domains or different customers.  Were there no issues like how many
such LMTP session there would have to be for a multiple RCPT message, I could
see that the MTA could do this.  Then for each RCPT received on SMTP and passed
to the appropriate LMTP session, the LMTP session response can then be sent back
to the SMTP sending client.  If one user does not exist but another user does,
even if on a different LMTP session, it pass those responses back on SMTP as an
error to one RCPT and an OK to another RCPT.  So in theory if the LMTP servers
decided to not accept the mail based on the filtering rules for that specific
user, then it can given a 5XX response which would be passed back on SMTP.

The question is, what MTAs go to that extreme, and do they have to be specially
configured and/or patched to do so.

-- 
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| Phil Howard - KA9WGN |   Dallas   | http://linuxhomepage.com/ |
| phil-nospam at ipal.net | Texas, USA | http://ka9wgn.ham.org/    |
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