OpenChange is an open-source implementation of the MAPI protocols on which Microsoft Exchange is based. With OpenChange you can develop non-proprietary tools to interact with or control Exchange systems, even on non-Windows sytems.

You can integrate OpenChange into a corporate environment, and even transparently replace an Exchange server with OpenChange and Samba.

This book explains the MAPI protocols and how OpenChange implements them, and goes on to show how you can use OpenChange tools, and develop new ones using the OpenChange libraries. The OpenChange Proxy lets the network manger mix MAPI with other systems, or extend Exchange features with Open Source components. For example, mail can be spam-filtered with DSPAM/SpamAssassin or antivirus-scanned with ClamAV.