Hi,is there a way to automatically exchange the address book with an another company? We are the same company but in different cities. For interconnection we are using VPN for Voice and Mail. The mail server is at the other company (exchange server). Access to the server is possible through VPN and WEB. Any help is appreciated.

Probably you need to go for MIIS to exchange the GAL between two forests. http://technet.microsoft.com/en-us/miis/default.aspx