Exchange: MAPI over HTTP

Messaging Application Programming Interface (MAPI) over HTTP is a transport protocol that 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.

MAPI over HTTP is a new transport used to connect Outlook and Exchange. MAPI/HTTP was first delivered with Exchange 2013 SP1 and Outlook 2013 SP1. MAPI/HTTP removes the complexity of Outlook Anywhere’s dependency on the legacy RPC technology.

Client requirements: Outlook 2016, Outlook 2013 SP1, Outlook 2010 with KB2899591 installed.

Server requirements: Exchange 2016, Exchange 2013 SP1.

In Exchange Server 2016, MAPI over HTTP is enabled by default at the organization level. In Exchange Server 2013 SP1 isn’t enabled and administrators will have to configure MAPI over HTTP.

Virtual directory configuration

Set-MapiVirtualDirectory -InternalUrl –ExternalUrl -IISAuthenticationMethods Negotiate

Certificate configuration

Certificate must include domains from InternalUrl and ExternalUrl, e.g.

Enable MAPI over HTTP

Enable for entire organization:

Set-OrganizationConfig -MapiHttpEnabled $true

Enable for indiviadual mailbox:

Set-CasMailbox -id <mailbox> -MapiHttpEnabled $true

Connection settings made at the mailbox level take precedence over any organization-wide settings.

Test MAPI over HTTP connections

Test-OutlookConnectivity -RunFromServerId <YourMailServer> -ProbeIdentity OutlookMapiHttpSelfTestProbe

Outlook connection status

RPC connection:


MAPI over HTTP connection:


Web browser check

Follow URL


Log paths

CAS: %ExchangeInstallPath%\Logging\HttpProxy\Mapi\

Mailbox: %ExchangeInstallPath%\Logging\MAPI Client Access\

Mailbox: %ExchangeInstallPath%\Logging\MAPI Address Book Service\


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