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
