[Dovecot] Strange Dovecot Issue

[Scott Hughes]

Greetings,

I am trying to copy email from one server to another server using 
Thunderbird.  The old server is a closed source ModusMail server and the 
new server is a Qmail server running Dovecot 1.2.3 (yes, I realize this 
is behind the times a bit).

My issue is this: Whenever Thunderbird gets to a message that has been 
forwarded (has the forward flag set) an error is generated from the new 
server (dovecot) that it does not know how to handle the forward flag.

Is this a known issue or is it simply that my version of Dovecot is behind?

Thanks,
Scott