Link Server is a free add-on tool for Outlook Messenger, which can be used for a Virtual Private Network & a Sub Network Office.
Link Server Tool can also be used in a single network, if you have problems with users displaying randomly on each refresh.
Link Server can run in:
Lite Server Mode - Helps to link users. Data transfer is made directly between users (not recommended for VPN). OR
Central Server Mode - helps to link users. Also ALL communications are made via Link Server (Recommended for VPN & large networks).