[Imap-protocol] Thunderbird confused by post-authenticate CAPABILITY change?

[Bill Janssen]

Interesting problem.  I'm sending three distinct sets of CAPABILITY
now.  Before the channel is encrypted, I send

(1) IMAP4rev1 LOGINDISABLED STARTTLS

After the channel is encrypted, but before any authentication, I send

(2) IMAP4rev1 SASL-IR AUTH=PLAIN

By the way, is this legal?  The server still supports STARTTLS, but it
will fail if used on an already-encrypted channel, so I figured I'd
omit it.

Anyway, after authentication, I send

(3) IMAP4rev1 NAMESPACE UIDPLUS IDLE

on the theory that an unauthorized client doesn't need to know that.
But I noticed that Thunderbird is never taking advantage of IDLE, even
though I've got the T-bird config box for it checked.

If I change (2) to be

(4) IMAP4rev1 SASL-IR AUTH=PLAIN NAMESPACE UIDPLUS IDLE

Thunderbird suddenly starts using IDLE.

Bill