Configure MAPI acceleration

Microsoft Outlook acceleration provides improved performance for traffic between Microsoft Outlook clients and Microsoft Exchange Servers, increasing throughput with a variety of optimizations, including data prefetching and compression.

This feature is also called “MAPI acceleration,” after the MAPI protocol used between Outlook and Exchange Server.

In networks where the Outlook data stream is unencrypted (the default before Outlook 2007), this feature requires no configuration.

In networks where the Outlook data is encrypted (the default with Outlook 2007 and later), acceleration can be obtained in one of two ways: by disabling encryption in the Outlook clients or by having the appliances join the Windows domain.

Supported outlook exchange versions and modes

Citrix SD-WAN WANOP appliances provide MAPI acceleration for Microsoft Outlook 2003-2016 and Exchange Server 2003-2010, in the following circumstances:

  • Any combination of supported clients and servers (using the MAPI protocol) is supported.

  • If the server-side appliance has joined a Windows domain, connections with MAPI encryption are accelerated. Otherwise, they are not, and encryption should be disabled in the Outlook clients.


    In Exchange Server 2013 the MAPI protocol changed to RPC over HTTP  protocol,  this protocol is supported. With Exchange Server SP1, the RPC over HTTP protocol changed to MAPI over HTTP protocol, this protocol is currently not supported.  


If your network uses encrypted Outlook data, which is the default setting in Outlook 2007 and later, you must implement one of the following prerequisites to make sure that MAPI connections are accelerated:


Outlook acceleration is a zero-configuration feature that is enabled by default. (If not wanted, it can be disabled by disabling acceleration on the MAPI service class on the Configuration: Service Class Policy page.) Outlook acceleration takes place automatically if the following conditions are met:

  • There is an appliance at the Exchange Server end of the WAN.

  • Either there is an appliance at the Outlook end of the WAN, or the system running Outlook is also running the Citrix SD-WAN WANOP Plug-in.

  • All Outlook/Exchange traffic passes through the appliances (or appliance and plug-in).

  • Either the Exchange Server or Outlook is restarted (acceleration does not begin until existing MAPI connections are closed).

  • Either encryption is disabled on Outlook, or the server-side appliance belongs to the Windows domain and has a secure peer relationship with the client-side appliance (or Citrix SD-WAN WANOP Plug-in). In the case where the appliance has joined the Windows domain, authentication on the domain must be kept at the default setting (negotiate), for acceleration to work.

Disable encryption on Outlook 2007 or Outlook 2010

Unless the server-side appliance has joined the Windows domain and has a secure peer relationship with the client-side appliance (or Citrix SD-WAN WANOP Plug-in), encryption between Outlook and Exchange Server must be disabled for acceleration to take place.

Encryption was disabled by default before Outlook 2007. Starting with Outlook 2007, encryption is enabled by default.

Performance note

MAPI uses a different data format from other protocols. This difference prevents effective cross-protocol compression. That is, a file that was first transferred through FTP and then as an email attachment does not receive a compression advantage on the second transfer. If the same data is sent two times in MAPI format, the second transfer receives full compression.

Configure MAPI acceleration