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One of the new and improved methods to connect Outlook 2013 clients to Microsoft Exchange 2013 SP1 is MAPI (Messaging Application Programming Interface) over HTTP (Hypertext Transfer Protocol).

It is a changeover from RPC/HTTP to MAPI/HTTP. MAPI over HTTP improves the stability of the Outlook and Exchange connections. MAPI/HTTP removes the complexity of Outlook Anywhere dependency on RPC.

Uses of MAPI over HTTP:

=>MAPI/HTTP reduces the amount of time user waiting for outlook to connect.

=>Enables authentication by using an HTTP based protocol.

=>Faster reconnection in case of any communication break because it’s only TCP connections.

=>When we change to a different network, the server maintains the session context for a configurable period of time.

How it works?

If simplified this is how it works:

Outlook Client begins an Autodiscover POST Request (When the request is sent by the Outlook a new attributeX-MapiHTTPCapability =1 for MAPi/HTTP is sent) => Exchange Server receives the connection & sees that it is coming from a MAPI/HTTP client & responds as how to connect using MAPI/HTTP => In response to the request Outlook is prompted for a restart (only the first time), post which Outlook uses MAPI/HTTP for communication with the Exchange Server.

So how do we configure MAPI/HTTP & what are the requirements?

Requirements:

=> All Exchange 2013 Client Access Servers should be update to Exchange Server 2013 SP1 or later.

=> All the clients must have Office 2013 SP1 recommended to be updated with the latest patch.

=> On the Exchange Servers that are not running on Windows 2012 R2, you will have to upgrade the Microsoft .NET Framework to 4.5.1.

=> We need one of the following Hotfix for .NET Framework 4.5.1 on all Exchange 2013 SP1 servers according to the OS version:

Windows Server 2012 R2

http://support.microsoft.com/en-in/kb/2908387

Windows Server 2012

http://support.microsoft.com/en-in/kb/2908385

Windows Server 2008 R2 Service Pack 1

http://support.microsoft.com/en-in/kb/2908383

=>Add the following Registry Key on all the Exchange Server 2013 Client Access Servers:

HKLMSoftwareMicrosoft.NETFramework => create a new DWORD with the name “DisableRetStructPinning” with value 1.

=> Add the following in all the CAS servers:

Open command prompt=> type systempropertiesadvanced => click Environment Variables => Under
system variables section click New => Variable name “COMPLUS_DisableRetStructPinning” => Set Variable Value 1 => Click Ok.

How to Configure MAPI/HTTP?

=> Create a Virtual Directory on the Exchange Server (we need to create the Virtual Directory for both Internal & External Directory)

Set-MapiVirtualDirectory -Identity “Domainmapi (Default Web Site)” -InternalUrl https://domain.com/mapi -IISAuthenticationMethods Negotiate

=>The certificate used in the Exchange servers must have the internal url & external url specified while creating MAPI virtual directory.

=>Make sure the Firewalls, proxyservers, Load balancers are all configured to allow acess to MAPI/HTTP directories.

=> Run the following command to enable MAPI over HTTP. After running this command the clients will a prompt to restart outlook to use MAPI/HTTP:

Set-OrganizationConfig -MapiHttpEnabled $true

=> Finally to test the MAPI/HTTP we can run the following command:

Test-OutlookConnectivity -RunFromServerId ContosoMail -ProbeIdentity OutlookMapiHttpSelfTestProbe

=> The Logs for the MAPI/HTTP can be seen in the following location:

ExchangeInstallPathLoggingMAPI Address Book Service

ExchangeInstallPathLoggingMAPI Client Access

ExchangeInstallPathLoggingHttpProxyMapi

Points to Note:

=> If we enable MAPI/HTTP, Outlook 2013 SP1 that connects through the Exchange 2013 SP1 will not be able to access public folders in the same forest of earlier versions of Exchange (Exchange 2007/Exchange 2010). It is not recommended to enable MAPI over HTTP until the Public Folders are moved to Exchange 2013 Server.

=>Also check if all the client machine that is running Outlook 2013 has the trusted certificate installed & make sure there are no certificate errors.

=>After enabling MAPI/HTTP is you want a client to use RPC /HTTP you can use the following registry key. This will not take effect until the exchange servers attempts another query for AutoDiscovery.

HKEYCURRENTUSERSoftwareMicrosoftExchange => create a new DWORD “MapiHttpDisabled” with value 1.

To enable the MAPI/HTTP back delete the above Key or set the Value to 0.

Ratish Nair

Microsoft MVP | Exchange Server

Team @MSExchangeGuru

Posted March 30th, 2015 under CAS, Exchange 2013, Outlook. RSS 2.0 feed. Leave a response, or trackback.