Open Outlook 2000 mail message very slow

When I open Outlook 2000 mail message, the response from Exchange server is almost very slow. (Note : the PC client’s and MS Exchange server are located difference sites. There are connected by 256K WAN link. The PC client’s is using MS Exchange server service setting.) Have any methods to improve the access speed ? Have any monitoring tools for this case? I want to take a record after and before improvement result.