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Date: Fri, 28 Feb 2003 23:55:57 +0300
From: Solar Designer <solar@...nwall.com>
To: popa3d-users@...ts.openwall.com
Subject: Re: Outlook 2002 duplicate emails

On Fri, Feb 28, 2003 at 11:57:30AM -0600, Thomas Hays wrote:

Hi,

> Here is a sample mbox file that I am using to reproduce the error:
> http://gold.aegisgroup.com/test.bad.gz

I've looked at this mbox (thank you for the very detailed problem
report!) and this is a problem with interaction between your Postfix
install and popa3d, not a problem with Outlook 2002 (although it could
be smarter at handling the situation).

Basically, because popa3d does not want to alter message sizes just to
record a Status: or an X-UIDL: header (like some other POP3 servers
do), it relies exclusively on message headers to produce unique IDs
(for UIDL command output).  In your case, Postfix has produced two
messages that are exactly the same (all header and body lines are the
same, byte to byte).  This has resulted in duplicate "unique" IDs
which, while an allowed behavior per RFC 1939 (*), is not good.

My opinion is that this should be dealt with in Postfix.  I did test
Postfix for this property previously and my results were different
from yours (qmail had the unfortunate property, while the versions of
sendmail and Postfix that I've tested didn't).  What version of
Postfix are you using?  Could you share the details of how the two
mail aliases are setup?

BTW, I have a qmail 1.03 patch which solves this by adding an
X-Delivery-ID: header, which popa3d is prepared to handle.  I should
probably make it available.

(*) The RFC says:

"         While it is generally preferable for server implementations
          to store arbitrarily assigned unique-ids in the maildrop,
          this specification is intended to permit unique-ids to be
          calculated as a hash of the message.  Clients should be able
          to handle a situation where two identical copies of a
          message in a maildrop have the same unique-id."

-- 
/sd

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