Re: [courier-users] Courieresmtp and 450 errors

[Lindsay H. <fmo...@fm...>]

On Tue, 2012-08-21 at 06:57 -0400, Sam Varshavchik wrote:
> Lindsay Haisley writes:
> 
> > Sam, et al,
> >
> > Here's a situation that happened recently.  I posted to a popular
> > mailing list and courieresmtp logged the following.
> >
> > Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD. 
> > 00006F31,from=<fmo...@fm...>,addr=<mai...@py...>:  
> > 450-4.3.2 Service currently unavailable
> > Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD. 
> > 00006F31,from=<fmo...@fm...>,addr=<mai...@py...>: 450  
> > 4.3.2 Contact your postmaster/admin for assistance. Please provide the  
> > following information in your problem report: time (A...
> > Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD. 
> > 00006F31,from=<fmo...@fm...>,addr=<mailman- 
> > us...@py...>,status: deferred
> >
> > The connecting server at python.org returned a temporary error.
> > Apparently Courier queued this email for redelivery, and the MUA
> > (Evolution) noted the failure and apparently left the problem email in
> > my Outbox.
> 
> Not possible. If Courier already has this message, the MUA must've sent it,  
> and, as far as the MUA is concerned, the message has been sent to the mail  
> server.
> 
> A MUA has absolutely no means, whatsoever, to know anything about the  
> message after it sent it to the mail server. Once Courier receives a  
> message, it acknowledges it with a 2xx. It does not wait and try to forward  
> the message, before acknowledging it.

OK, a little work with tcpdump and swaks clarified how things actually
work.  The designated SMTP server for the MUA engages in _two_ SMTP
dialogs, one with them MUA and one with the recipient mail server.

Please excuse me.  I don't deal enough with relaying to be fully
familiar with the way things work.  Usually I'm testing the MDA and
connect with the MTA on the same box.

Is there any possibility that Courier, when relaying, might hold open
the connection with a requesting MUA until the connection with the
recipient server is complete, and return something to the MUA
accordingly?  In particular, is there any difference in the behavior of
Courier when a recipient server returns a 450 tempfail, as opposed to a
451 code?

> >  A minute later, the MUA tried again, successfully:
> >
> > Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD. 
> > 0000000050318F21.00006FAC,from=<fmo...@fm...>,addr=<mailman- 
> > us...@py...>: 250 2.0.0 Ok: queued as 3X0cTL2xBFzQM6
> > Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD. 
> > 0000000050318F21.00006FAC,from=<fmo...@fm...>,addr=<mailman- 
> > us...@py...>,size=4147,success: delivered: mail.python.org  
> > [82.94.164.166]
> > Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD. 
> > 0000000050318F21.00006FAC,from=<fmo...@fm...>,addr=<mailman- 
> > us...@py...>,size=4147,status: success
> 
> This is Courier sending a different message. This is not your MUA.

Well I suspect it _was_ the MUA which inserted this since this message
was identical in all respects to the previous one, except for the
assigned message ID, and the list subscribers received two identical
posts from me.  The message IDs back this up.  I'm very fond of my
chosen MUA, Evolution, which is nearly as powerful for mail management
as some of the old CLI mail programs such as Mutt.  T-bird can't touch
it, although with recent improvements it's getting there.  Evolution
does, however, have "issues", which is probably a good part of the
reason it's no longer the default MUA for recent versions of Ubuntu
Linux.

-- 
Lindsay Haisley       | "Everything works if you let it"
FMP Computer Services |
512-259-1190          |          --- The Roadie
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