Slow connection on startup: Outlook 2003 - Exchange 2003

[Samshen]

Hi all,
I have Exchange 2003 server and clients running Outlook 2003 client in non-cache mode.
When starting up, there is a delay of 1 or 1:30 minutes. When I change to cache mode, outlook starts up normally, but in the right lower corner is displayed the message: "trying to connect" and after 1 minute the folder synchronization begins.
So it is clear that the startup connection is very slow. And time after time in this corner is displayed the message: "Outlook is trying to retrive data from the server".
Can anyone help me, why this connection is very slow? I test the connection between my pc and the server by exchanging some hundered mega of files and everything goes OK.
Any idea will be very appreciated.
Samshen.