[Dovecot] Thunderbird saved searches, tags and Dovecot oddity

[Michael Durket]

In converting everyone at our site from UW-IMAP I've run into a  
problem with a few
Thunderbird users and I'm wondering if anyone has some recommendations.

We're running dovecot 1.0.13 (yes I know it's old but we don't upgrade  
production
facilities that often). The affected Thunderbird users are running  
version 2.0023.

What's happening is this:

     1) The user creates a filter rule which looks for, say, the From:  
header on a
          message, and then tags that message with a Thunderbird tag  
that they've
          defined (in this case "ToDo").

     2) The user also defines a search folderthat shows all mail items  
tagged "ToDo".

     3) Every day, the user opens the folder, handles all the ToDo  
messages and
          untags them as they are handled, causing them to disappear  
from the
          folder.

     4) The next day (or the next time Thunderbird is started), all  
the previously
          tagged messages are back (in addition to newer ones).

  This doesn't happen with UW-IMAP (version imap-2007e which I think  
is the
last version with bug fixes ever issued). I haven't traced out the  
IMAP commands
going back and forth yet to see what might be different between the  
two servers -
I thought I'd ask here first to see if this is a known issue for which  
there is a solution
(like upgrading dovecot to a specific version).