[RFC 5162] QRESYNC: Clarification on CLOSED response

[Alexey Melnikov]

Hi Thomas,

> On 20 Feb 2014, at 09:25, Thomas Jarosch <thomas.jarosch at intra2net.com> wrote:
> 
> Hello Alexey and Dave,
> 
> after updating an IMAP server to a version supporting QRESYNC,
> we started facing unexpected issues with one client.
> (server: cyrus-imapd 2.4.17, client: "c-client" from Mark Crispin)
> 
> Of special interest became the "CLOSED" response: RFC 5162, sect 3.7
> states that any server implementing the QRESYNC extension must send
> the CLOSED response on mailbox changes via SELECT/EXAMINE.
> 
> This seems to happen unconditionally, regardless
> if the client enabled QRESYNC or CONDSTORE.
> 
> 
> Unfortunately the c-client IMAP implementation uses a fake "CLOSED" response 
> internally to mark a connection as broken -> the client goes "offline" 
> during a folder change. Clearly the client needs to be fixed since RFC 3501 
> states: "Client implementations SHOULD ignore response codes that they do 
> not recognize."
> 
> 
> *** The big question ***
> Was it intentional that the CLOSED response should always be sent?

Yes.

> If yes, what was the intention?

As CLOSED signals the exact moment after which the old mailbox is closed, I think it has more general use.
I wish we thought about CLOSED when updating the base IMAP spec. It should have been a base spec feature.

> May be the wording can be clarified a bit before the updated RFC is final:
> Should the server send the CLOSED response even if QRESYNC is not enabled?

I will check and update. Thank you for the comment!

Best Regards,
Alexey
> 
> Best regards,
> Thomas Jarosch
>