[Imap-protocol] Unsolicited server responses
arnt at gulbrandsen.priv.no
Fri Nov 30 03:56:24 PST 2018
>> Given that the server can unilaterally send updates to the
>> client, why was the IDLE extension useful/necessary?
> I'm no expert but I don't think I have seen an IMAP server that
> sends unsolicited EXISTS or EXPUNGE responses when not in IDLE
I've co-written one that sends a sends a very small number of responses and
then stops, which hasn't caused problems. I've heard that another server
sent an unlimited number of responses using blocking i/o, and that would
cause problems if the client wasn't listening.
IIRC more servers send unsolicited responses occasionally, to keep NAT
middleboxes from discarding the connection.
> "While the spec [RFC3501 I assume] actually does allow a server
> to push EXISTS responses asynchronously, a client can't expect
> this behavior and must poll."
That's the key.
More information about the Imap-protocol