Kolab has stopped receiving mail

[Simon Powell]

Odd one here folks.
Kolab lets me login to mailbox, lets me send mail out but doesn't  
receive mail - nor does it seem to reject it. A snippet from /usr/ 
local/kolab/postfix/log/postfix.log shows the following(names changed  
to protect the stupid):-

Apr 26 09:50:56 kolab.myserver.org.uk <info> postfix/qmgr[4987]:  
373161386F2: to=<root at myserver.org.uk>, orig_to=<root>, relay=none,  
delay=136256, status=deferred (delivery temporarily suspended:  
transport is unavailable)
Apr 26 09:51:56 kolab.myserver.org.uk <warning> postfix/qmgr[4987]:  
warning: connect to transport kolabfilter: Connection refused


If I connect manually to smtp everything looks in order and I can hand  
roll an email.....however it says it is queued for delivery.....then  
disappears into the ether. This has randomly started happening a few  
days ago so I would like to get it resolved as who knows what 'vital'  
email I could be missing out on....... :-)
If anyone has any clue please drop me a line.
Cheers
Si