By Paul DeGroot [bio]
Posted: May 26, 2008

The following is an illustration accompanying an article published by Directions on Microsoft, an independent research firm focused exclusively on Microsoft strategy & technology. More samples of our content, as well as a list of upcoming articles and reports are also available.

Upgrading a server in one location can trigger a requirement that users who don't access the server directly must nonetheless upgrade their Client Access Licenses (CALs).

In this case, the Tokyo office of a global corporation has upgraded from Exchange Server 2003 to Exchange Server 2007and has upgraded its CALs accordingly. The New York office, which uses Exchange Server 2003, is also required to upgrade to Exchange 2007 CALs. The reason: Microsoft deems that use of the Microsoft Messaging API (MAPI) on network links between the two offices creates indirect access, through multiplexing or pooling, between the New York clients and the Tokyo servers. However, because the Hong Kong office communicates with the Tokyo office with the Simple Mail Transport Protocol (SMTP), the connection does not trigger a requirement for upgraded CALs.