[RFC 5162] QRESYNC: Clarification on CLOSED response

[Thomas Jarosch]

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?
If yes, what was the intention?

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?

Best regards,
Thomas Jarosch