nnimap fails with TLS error when trying to open a davmail server

[Steinar Bang <sb@dod.no>]

Platform: Intel P4,
	  debian testing ("jessie"),
          GNU Emacs 24.3.1 (i486-pc-linux-gnu, GTK+ Version 3.4.2) of 2013-04-13 on murphy, modified by Debian
          libgnutls26:i386 2.12.20-6
          Ma Gnus v0.8
          davmail 4.3.1-2134-1


I have started a davmail http://davmail.sourceforge.net/ server that
talks to an Exchange server.  But nnimap fails when trying to open the
IMAP server presented by davmail.

Here is the server definition (created in the server buffer, not as a
select method):
 (nnimap "davmail"
         (nnimap-server-port 1143)
         (nnimap-address "localhost")
         (nnimap-stream starttls))

The error message from the Messages buffer, is:
 Opening connection to localhost...
 Unable to open server nnimap+davmail due to: Buffer  *nnimap localhost 1143  *nntpd**-720412 has no process


If I change the server definition to
 (nnimap "davmail"
         (nnimap-server-port 1143)
         (nnimap-address "localhost")
         (nnimap-stream ssl))
or
 (nnimap "davmail"
         (nnimap-server-port 1143)
         (nnimap-address "localhost")
         (nnimap-stream tls))

then I get the following error message in the Messages buffer (the same
error message for both of the above nnimap-stream values):

 Opening connection to localhost via tls...
 gnutls.c: [0] (Emacs) fatal error: An unexpected TLS packet was received.
 gnutls.el: (err=[-15] An unexpected TLS packet was received.) boot: (:priority NORMAL :hostname localhost :loglevel 0 :min-prime-bits 256 :trustfiles (/etc/ssl/certs/ca-certificates.crt) :crlfiles nil :keylist nil :verify-flags nil :verify-error nil :verify-hostname-error nil :callbacks nil)
 Unable to open server nnimap+davmail due to: GnuTLS error: #<process *nnimap*<1>>, -15
gnutls.c: [0] (Emacs) fatal error: An unexpected TLS packet was received. [100 times]
indent-relative: Buffer is read-only: #<buffer *Server*>

Does anyone know what might cause this?  Has anyone else had any success
with davmail?

Thanks!


- Steinar