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Re: IDLE and idle
On Wed, 22 Nov 2006, Arnt Gulbrandsen wrote:
RFC 3501 section 5.3 permits a server to send untagged unsolicited
EXISTS responses to a client even when it's not processing any command,
under certain circumstances.
Correct.
This was supposed to be the "correct" behavior for servers, all "good"
servers and clients would be fully asynchronous.
I knew that this was asking for trouble; I remembered the deadlock
problems with the CCA Datacomputer all too well. The practice of polling
using NOOP (and thus indicating client readiness to accept unsolicited
server data) was implemented from the onset. Later on, IDLE also resulted
from this realization.
However, the political environment at the time did not accept reality.
The specification's allowing of unsolicited data outside of a command was
an attempt at placation. It failed to placate and the RFC 1203 ("IMAP3")
fork resulted (the fork was stillborn, but it caused years of FUD).
I really wish that we remove this from IMAP, but I'm sure that someone
would cry foul.
I'm not familiar with any servers that do this. (UW sends OK, but my
question is about EXISTS.) Are there any that send EXISTS, and if so,
which?
UW imapd can send BYE outside of a command. Do you have an example of OK
outside of a command? I can't think of any.
But there's something else that clients must consider. See my forthcoming
response to Dave's message.
-- Mark --
http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.