dovecot - Sep 2009 - Sieve not fast enough after upgrade?

I've upgraded mine Dovecot 1.0.15 to 1.2.4 also moved to new Sieve. I 
have simple sieve rule:

if header :contains "Delivered-To" ["bcc at bcc.inblock.ru"]
{
         setflag "\\Seen";
}

It basically mark my own messages which are saved to Sent folder. When I 
was on 1.0.15 I never seen unread count in Thunderbird, but suddenly 
after upgrade I seen unread message in Sent folder just after I've sent 
message. If I open Sent folder it already marked as read.
Me wonder if this is actually Dovecot much faster delivers and reports 
to MUA there is new unread message or Sieve not perform fast enough?

On Sep 15, 2009, at 7:27 PM, Nikolay Shopik wrote:
> I've upgraded mine Dovecot 1.0.15 to 1.2.4 also moved to new Sieve.  
> I have simple sieve rule:
>
> if header :contains "Delivered-To" ["bcc at
bcc.inblock.ru"] {
>        setflag "\\Seen";
> }
>
> It basically mark my own messages which are saved to Sent folder.  
> When I was on 1.0.15 I never seen unread count in Thunderbird, but  
> suddenly after upgrade I seen unread message in Sent folder just  
> after I've sent message. If I open Sent folder it already marked as  
> read.
> Me wonder if this is actually Dovecot much faster delivers and  
> reports to MUA there is new unread message or Sieve not perform fast  
> enough?
The \Seen flag is set before the message is visible, so I can't really  
think of why this would be happening. Getting a rawlog from when TB  
sees this might be helpful. http://wiki.dovecot.org/Debugging/Rawlog