[Dovecot] Proxy problems with 1.0.5 !

[Ed W]

Hi

I am trying to do a staged migration over to dovecot, but having 
troubles at the first hurdle.  I setup the proxy feature to redirect 
most of our users back to the current Courier imap/pop server, and it's 
partly working, but I'm getting some serious errors using Thunderbird 
and IMAP.

Now, I had expected the proxying to be fairly transparent and basically 
just dovecot doing an auth and then passing the stream on to the other 
server?  My problem is that using Thunderbird I can read all my folders 
OK, but I can't save anything in my Sent Items or Drafts folders...  
Basically I get errors every time I try and send an email, or try to 
save to the draft folder. 

Curiously, directly browsing into those folders works fine, as does 
deleting emails, and apparently copying them works fine also...  Why is 
the saving of sent messages failing...?

The setup is basically taking a working Thunderbird install, changing 
the server name from pointing at the Courier server to point at the 
dovecot server - dovecot in turn is told to proxy back to the original 
server. 

All I'm getting from Thunderbird is an "Invalid Command" response.  Is 
there an easy way to get a look inside the imap stream to try and see 
what's failing?

Any suggestions on why this is happening at all? 

One idea is that I have setup completely different namespaces in 
Dovecot, (with a hidden namespace which should be courier compatible), 
but I wouldn't have expected this to affect the Proxy stuff at all?!

Grateful for any pointers to debug this - it's a fairly major hurdle for 
my rollout

Thanks

Ed W