[Dovecot] IDLE dropping EXISTS events on mass message arrival

[Michael M Slusarz]

Quoting Eric Wong <normalperson at yhbt.net>:

> Hi, I'm not sure if this is some throttling/DoS protection or a bug.  I
> didn't see notice anything like it mentioned looking at the NEWS file
> from hg, this is on 2.1.7 on Debian stable.
>
> I have a client doing IDLE on INBOX.vomiteer.  When individual messages
> arrive with some time interval in between them, I get EXISTS events for
> each message as expected.
>
> However, when I store a bunch of messages at once (via tag + mass copy
> in mutt on a fast-ish connection), I get a few EXISTS events (sometimes
> one, sometimes two) even though I copied a lot of new messages over.
>
> I expected to get an EXISTS event for each message which arrived, but
> perhaps there's some sort of DoS/throttling mechanism.

This is correct IMAP behavior.  EXISTS is defined as enumerating the  
current number of messages in the mailbox.  Nowhere in the RFC does it  
say that a separate EXISTS is needed for every message added.

michael