SteelHead™ Deployment Guide - Protocols : Microsoft Exchange Email Optimization
Microsoft Exchange Email Optimization
This chapter describes the optimization of the Messaging Application Programming Interface (MAPI) used between Microsoft Outlook clients and Exchange servers. The combination of Outlook and Exchange server is one of the most common client and server combinations for email in a corporate business environment. This chapter includes the following sections:
  • MAPI Client and Server Communication
  • RiOS MAPI Optimization
  • MAPI over HTTP
  • MAPI Destination Port Handling
  • MAPI Multiple Context
  • The MAPI communication mechanism is also known by a more recent name: Microsoft as Outlook-Exchange Transport Protocol.
    MAPI comes in two forms: extended and simple. This chapter discusses the extended form, which is used by Outlook. The simple form is included as part of Microsoft Outlook Express and is not discussed here.
    In the last ten years, MAPI has evolved through Exchange v5.5, Exchange 2000, Exchange 2003, Exchange 2007, and Exchange 2010. Outlook versions have followed in close coordination. RiOS can perform optimization for each of these Exchange versions.
    For information about Exchange 2013, see Microsoft Exchange 2013 Optimization.
    Because of the requirements of Exchange 2003, the Exchange server communicates using an encrypted conversation with compatible versions of the Outlook client. By default, the encryption mode is enabled in Exchange 2007 and Exchange 2010. RiOS securely optimizes this encrypted MAPI traffic by using the RiOS MAPI optimization along with the Windows-domain related RiOS features.
    Microsoft Outlook Cache mode was introduced with Outlook 2003. Cache mode attempts to hide performance issues over the WAN by preemptively downloading new email and their attachments from the Exchange server to a cache of storage on the local hard disk of the Outlook client workstation. Although this gives an appearance of fast performance, it has no effect on emails going to the sent items or trash folder of the user. Using Cache mode also means that any mail, including unwanted or junk mail (and attachments), is downloaded to the Outlook client. RiOS provides optimization for Outlook clients using Cache mode, both by reducing the increased WAN bandwidth impact of Cache mode and decreasing the wait time for arriving and transmitted emails.
    For more information about configuring MAPI optimization, see the SteelHead Management Console User’s Guide.