[Imap-protocol] example of authentication PLAIN with imap?

[Bill Janssen]

I'm trying to figure out exactly how to implement PLAIN authentication
for IMAP.  The spec seems less than clear to me.  The example given in
RFC 2595, which is not for IMAP, illustrates a PLAIN exchange thusly:

C: a003 AUTHENTICATE "PLAIN" {21+}
C: <NUL>tim<NUL>tanstaaftanstaaf

That is, it's one message, giving two parameters, "PLAIN" and the
authentication information.

However, when I advertise AUTH=PLAIN, Thunderbird sends

C: 4 authenticate plain

without any authentication information.  This is in accord with the
general description of the AUTHENTICATE message in RFC 3501, and with
the examples of non-PLAIN authentication given in RFC 3501, but not in
accord with RFC 2595, which explicitly says "a single message", or with
the example given.

Bill