Please describe the problem:
Evolution fails to establish a TLS-secured session with my IMAP server. It then
*silently* falls back to clear text and transmits my password over the unsecured
connection!

The IMAP server is Courier IMAP; it logs the following error:
Apr 27 17:34:22 blah imaplogin: couriertls: accept: error:1408F10B:SSL
routines:SSL3_GET_RECORD:wrong version number

Since the server continually replies with 'NO STARTTLS required', it is
impossible to escape from the password dialog without having to kill
Evolution--as soon as I press cancel, it comes back, and this repeats forever.

Steps to reproduce:
1. Configure IMAP account to use TLS
2. Enter password at password prompt
3. Evolution issues the STARTTLS command, but then 
drops back to clear text when the TLS negotiation fails

Actual results:
Evolution sends my password out in clear text even though the server advertised
the LOGINDISABLED capability. According to RFC 2595 section 3.2:

   The current IMAP protocol specification (RFC 2060) requires the
   implementation of the LOGIN command which uses clear-text passwords.
   Many sites may choose to disable this command unless encryption is
   active for security reasons.  An IMAP server MAY advertise that the
   LOGIN command is disabled by including the LOGINDISABLED capability
   in the capability response.  Such a server will respond with a tagged
   "NO" response to any attempt to use the LOGIN command.

   ...

   An IMAP client which complies with this specification MUST NOT issue
   the LOGIN command if this capability is present.

Expected results:
Evolution should display an error message to the user and not fall back to a
clear connection.

I think there should also be some kind of indicator in the password dialog box
showing whether the connection is secured. An obvious indicator is a padlock
that appears locked/unlocked depending on whether the connection is secured or not.

Does this happen every time?
Yes

Other information:
Here is a transcript of the IMAP session:

####
T 1.2.3.4:143 -> 100.101.102.103:42060 [AP]
  * OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT
   THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS LOGINDISABLED] C
  ourier-IMAP ready. Copyright 1998-2004 Double Precision, Inc.  See COPYING
  for distribution information...
##
T 100.101.102.103:42060 -> 1.2.3.4:143 [AP]
  A00000 CAPABILITY..
##
T 1.2.3.4:143 -> 100.101.102.103:42060 [AP]
  * CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THR
  EAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS LOGINDISABLED..A0000
  0 OK CAPABILITY completed..
##
T 100.101.102.103:42060 -> 1.2.3.4:143 [AP]
  A00001 STARTTLS..
#
T 1.2.3.4:143 -> 100.101.102.103:42060 [AP]
  A00001 OK Begin SSL/TLS negotiation now...
##
T 100.101.102.103:42060 -> 1.2.3.4:143 [AP]
  .4..........................d..b......' Z[...V.....}..
#####
T 1.2.3.4:143 -> 100.101.102.103:42061 [AP]
  * OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT
   THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS LOGINDISABLED] C
  ourier-IMAP ready. Copyright 1998-2004 Double Precision, Inc.  See COPYING
  for distribution information...
##
T 100.101.102.103:42061 -> 1.2.3.4:143 [AP]
  A00000 CAPABILITY..
##
T 1.2.3.4:143 -> 100.101.102.103:42061 [AP]
  * CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THR
  EAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS LOGINDISABLED..A0000
  0 OK CAPABILITY completed..
##
T 100.101.102.103:42061 -> 1.2.3.4:143 [AP]
  A00001 LOGIN user password..
#
T 1.2.3.4:143 -> 100.101.102.103:42061 [AP]
  A00001 NO STARTTLS required..
####
T 100.101.102.103:42061 -> 1.2.3.4:143 [AP]
  A00002 LOGOUT..

<repeats until I kill evolution>