OFFTOPIC Re: [Mailman-Users] Archive URL in postings (2.1b3)

J C Lawrence claw at
Thu Oct 31 09:39:50 CET 2002

On Wed, 30 Oct 2002 08:05:32 -0800 (PST) 
alex wetmore <alex at> wrote:
> On Tue, 29 Oct 2002, J C Lawrence wrote:
>> On Tue, 29 Oct 2002 10:56:39 -0800 (PST) alex wetmore
>> <alex at> wrote: 

>>> 1) You are using an email system which removes duplicates (based on
>>> the Message-Id header).  Microsoft Exchange 2000 is one such system.
>>> If Mailman is changing the headers so much perhaps it should stick a
>>> new Message-Id on the message though.

>> We should start out admitting that such mail systems are broken and
>> then decide how far we want to cater to such broken systems.

> Eliminating duplicates is a useful feature, not a broken one.  

My original statement was more generous than I intended.  Corrected:

  MTAs which do duplicate suppression are broken.  That's the function
  of the MUA, or, in very constrained instances, the LDA.

> Think about the hacks that Mailman-2.1 has to prevent sending the
> duplicate.  

Yup.  I'm not fond of their existence.

> In a complex corporate topology there are reasons why duplicates are
> sometimes generated, but clients should have no reason to see them.

Then they configure their MUAs not to.

> Exchange is not the only system that does this, but it might be the
> widest deployed.

FWLIW Cyrus can do dupe suppression at the LDA level.  Sadly its a
global setting.

>> There are multiple ways to achieve this.  Parsing To: is one of the
>> more fragile ways.  Far more effective and near-guaranteed to be
>> correct (except for the standard broken software case as above) is
>> tracking In-Reply-To: from your original post(s).

> That depends on keeping a database of sent message-ids and comparing
> In-Reply-To against each of them.  Few clients support this.

Ignoring the closed source or otherwise opaque cases (ie no LDA/MDA
control): tracking In-Reply-To: headers is neither complex or expensive.
I do it here and have done for years.

Counting the opaque and transparent cases: Partially true.  Most MUAs
will happily thread under your original message.

  Note to self: Must investigate doing this sort of thing under Sieve.
  I'm fairly sure it's not possible (need to escape the Sieve sandbox
  for localFS access).

> If you can recommend a decent text-based IMAP client that runs on Unix
> and Win32 and which supports this functionality I'm all ears.

Sorry, I don't track the Windows state of affairs.  Its been 12 years
since I used windows anything more than trivially and I've no interest
in changing that.

J C Lawrence                
---------(*)                Satan, oscillate my metallic sonatas. 
claw at               He lived as a devil, eh?  Evil is a name of a foeman, as I live.

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