Re: [sieve] Fwd: New Version Notification for draft-bosch-sieve-duplicate-02.txt

Stephan Bosch <> Fri, 03 May 2013 08:40 UTC

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Date: Fri, 03 May 2013 10:40:02 +0200
From: Stephan Bosch <>
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To: Ned Freed <>
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Subject: Re: [sieve] Fwd: New Version Notification for draft-bosch-sieve-duplicate-02.txt
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Op 4/25/2013 11:44 PM, Ned Freed wrote:
>> One other thing: we recently defined this great new Sieve use-case
>> called IMAPSieve. Is there any application imaginable for the duplicate
>> test in this context, i.e. do we want to allow it there? Either way, I
>> think we should state its applicability explicitly.
> I think there are legitimate use-cases, but it's also incredibly easy 
> to misuse
> in this context.
> The basic problem is that moving messages around in IMAP doesn't carry 
> with it
> any sort of inherent special semantic and people move messages around 
> for all
> sorts of reasons (or for no real reason at all). This is quite unlike 
> message
> delivery.
> So, for example, you could define a Sieve in IMAP to prevent, say, the
> inclusion of a second copy of the same message in a given folder. But bad
> things are going to happen if, say, you forget the filter is there and 
> move
> some of the messages out and back in a couple of times.
> We'd have to extend the semantics of the extension substantiantially 
> to take
> care of this, and even if we were to do that actually using it would be
> very tricky indeed.
> Since I see the main benefit of this extension as how simple it makes
> duplicate checks in Sieve, this usage makes me very nervous, so nervous
> that I could certainly accept a "NOT RECOMMENDED" label for this case.

Yes, I agree with that.

BTW, any further comments on the document as it is now? More thoughts on 
the ':last' issue?