MAPI over HTTP

What is mapi over http

Messaging Application Programming Interface (MAPI) over HTTP is a new transport protocol implemented in Microsoft Exchange Server 2013 Service Pack 1 (SP1). MAPI over HTTP improves the reliability and stability of the Outlook and Exchange connections by moving the transport layer to the industry-standard HTTP model. This allows a higher level of visibility of transport errors and enhanced recoverability. Additional functionality includes support for an explicit pause-and-resume function. This enables supported clients to change networks or resume from hibernation while maintaining the same server context.

Implementing MAPI over HTTP does not mean that it is the only protocol that can be used for Outlook to access Exchange. Outlook clients that are not MAPI over HTTP capable can still use Outlook Anywhere (RPC over HTTP) to access Exchange through a MAPI-enabled Client Access server.

Benefits of MAPI over HTTP

• Enables future innovation in authentication by using an HTTP based protocol.
• Provides faster reconnection times after a communications break because only TCP connections—not RPC connections—need to be rebuilt. Examples of a communication break include:
• Device hibernation
• Changing from a wired network to a wireless or cellular network
• Offers a session context that is not dependent on the connection. The server maintains the session context for a configurable period of time—even if the user changes networks.

Prerequisites

1. Upgrade Outlook clients to Outlook 2013 SP1 or Outlook 2010 SP2 and updates KB2956191 and KB2965295 (April 14, 2015).
2. Upgrade Client Access and Mailbox servers to Exchange 2013 SP1

Note : All Client Access servers must be upgraded to Exchange 2013 SP1 before enabling MAPI over HTTP. Otherwise, Outlook can fail to connect to mailboxes.
Failure to upgrade the all the Mailbox servers in a Database Availability Group (DAG) can result in email delays and a client requirement to restart Outlook in case of a database failover.

3.       On all Exchange 2013 servers, you need to install Microsoft .NET Framework 4.5.2

4.     On all Exchange 2013 SP1 Client Access servers, add the COMPLUS_DisableRetStructPinning Windows environment variable by performing the following steps.

a.     In a Command prompt window, run systempropertiesadvanced and click Environment Variables.

b.     In the System variables section, click New and enter the following information.

o    Variable name   COMPLUS_DisableRetStructPinning

o    Variable value   1

c.     When you are finished, click OK.

How to configure MAPI over HTTP

1.       Virtual directory configuration   Bydefault, Exchange 2013 SP1 creates a virtual directory for MAPI over HTTP. You use the Set-MapiVirtualDirectory cmdlet to configure the virtual directory. You must configure an internal URL, an external URL, or both

Set-MapiVirtualDirectory -Identity "Contoso\mapi (Default Web Site)" -InternalUrlhttps://Contoso.com/mapi -IISAuthenticationMethodsNegotiate

2.     Certificate configuration   The digital certificate used by your Exchange environment must include the same InternalURL and ExternalURL values that are defined on the MAPI virtual directory. Make sure the Exchange certificate is trusted on the Outlook client workstation and that there are no certificate errors, especially when you access the URLs configured on the MAPI virtual directory.

3. Update server rules   Verify that your load balancers, reverse proxies, and firewalls are configured to allow access to the MAPI over HTTP virtual directory.
4. Enable MAPI over HTTP in your Exchange Organization

        Set-OrganizationConfig -MapiHttpEnabled $true

Test MAPI over HTTP connections

You can test the end-to-end MAPI over HTTP connection by using the Test-OutlookConnectivity cmdlet.

Test-OutlookConnectivity -RunFromServerId ContosoMail -ProbeIdentity OutlookMapiHttpSelfTestProbe

Logs for MAPI over HTTP activity are at the following locations:

• %ExchangeInstallPath%Logging\MAPI Address Book Service\
• %ExchangeInstallPath%Logging\MAPI Client Access\
• %ExchangeInstallPath%Logging\HttpProxy\Mapi\

Note: This will applicable to Exchange server 2016.