Re: [Extra] Martin Duke's No Objection on draft-ietf-extra-imap4rev2-25: (with COMMENT)

Martin Duke <> Sun, 24 January 2021 21:14 UTC

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From: Martin Duke <>
Date: Sun, 24 Jan 2021 13:14:18 -0800
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To: Bron Gondwana <>
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Subject: Re: [Extra] Martin Duke's No Objection on draft-ietf-extra-imap4rev2-25: (with COMMENT)
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Thanks Bron,

Your replies make sense, but one:

Regarding 4.1.1, I find this terminology confusing, overloading the word
"sequence", although at this stage maybe it can't be helped. Still, this
section still seems very unclear to me.

4.1.1 <>.
Sequence set and UID set

   A set of messages can be referenced by a sequence set containing
   either message sequence numbers or unique identifiers.  See Section
9 <>
   for details.  Sequence sets can contain ranges (e.g. "5:50"), an
   enumeration of specific message/UID numbers, a special symbol "*", or
   a combination of the above.

   A "UID set" is similar to the sequence set of unique identifiers;
   however, the "*" value for a sequence number is not permitted.

So if I got this right, there's a "sequence set" that contains either
sequence numbers or UIDs and can contain "*".
then there is also a "UID Set" which is UID only, and cannot contain "*".
But then I have two questions:
(1) Can a sequence set have a combination of sequence numbers and UIDs (" a
combination of the above")?
(2) If a UID set can't have sequence numbers, then why is it explaining the
lack of "*" in the context of UID sets with sequence numbers?

On Sat, Jan 23, 2021 at 7:14 PM Bron Gondwana <>

> On Sat, Jan 23, 2021, at 15:57, Martin Duke via Datatracker wrote:
> (I know the answers to these!)
> what would happen if the UID approached 2^32 due to a lifetime of
> spam
> or something? The server can increment the validity value, but doesn’t that
> make earlier email unreferenceable except via sequence number?
> Sequence number is even less persistent - but when you increment the
> UIDVALIDITY you can renumber the UIDs for everything, so you'd just start
> at 1 and reid all the existing records.  So they'll be referenceable by
> their new UIDs next time the mailbox is selected.
> And (plug) if the server implements RFC8474 (object ids) then a client can
> even tell that it's the same email and not need to fetch the content again,
> even after a UIDVALIDITY change.
> 2.3.2 In the $Phishing definition, do you mean the user agent SHOULD (in
> caps)
> display an additional warning message?
> This definition is copied from the IANA registry for keywords:
> I'm not sure there's any point in changing the text to be different from
> the IANA registration just to make it capital SHOULD.  It's unlikely to
> change anybody's behaviour on reading this document.
> 4.1.1 the last statement, “ the "*" value for a sequence number is not
> permitted.”, is oddly placed, enough that it almost reads like a typo
> where you
> meant UID. A clearer statement might be “The ‘*’ value is permitted for
> UIDs
> but not sequence numbers.”
> No, that would be an incorrect statement.  The phrase "UID set" is a
> definitional term which means:
> * a sequence set;
> * that references UIDs, not message numbers; and
> * that consists only of numbers, not the magic '*' character (which can
> change value as new messages arrive)
> You can have a "sequence set" which references UIDs and does contain '*',
> but then it's not a "UID set" any more by definition.
> Cheers,
> Bron.
> --
>   Bron Gondwana, CEO, Fastmail Pty Ltd