In this article we will have a look at the steps to configure MAPI/HTTP for all users in Exchange 2016 server.

We need to understand this point very clearly.

Since the MAPI/HTTP protocol is supported only from the Exchange 2013 with exchange 2016 & Exchange 2010 coexistence the behavior will be :

1. Exchange 2010 users will be getting the RPC/HTTP connections on their outlook.
2. Exchange 2016 users will be getting only MAPI/HTTP connections on their outlook.

Reason :

From Exchange 2013 we had an option to choose either RPC/HTTP or MAPI/HTTP .But from Exchange 2016 Microsoft has totally retired the legacy RPC protocol and wrapped them via MAPI/HTTP through which all the connections will be only via mapi/http.

In-order to accomplish this task you need to make few changes in exchange, firewall as well as DNS side.

So basically the connections will go like the below

For Exchange 2010 Users: 

From internet (RPC/HTTP) – Firewall receives/RPC requests – The request is forwarded to Exchange 2016 CAS services – Connections are proxied back to Exchange 2010 CAS server

For Exchange 2016 Users:

From Internet (MAPI/HTTP) – Firewall received /MAPI requests – The request is forwarded to Exchange 2016 CAS services – Connections are directed to Exchange 2016 Mailbox server.

Now lets see the steps that we need to do to accomplish this task:

On Exchange

1. Run the Command Set-MapiVirtualDirectory and set the external URL of MAPI virtual directory

Example:

Set-MapiVirtualDirectory -Identity “mapi (Default Web Site)” -InternalUrl https://contoso.com/mapi -IISAuthenticationMethods Negotiate,NTLM,OAuth

Better to keep the authentication negotiate for the legacy clients till the migration gets completed from Exchange 2010

If we could recollect for Exchange 2013 users we need to run this command to enable MAPIHTTP for end users

Set-OrganizationConfig -MapiHttpEnabled $true

Since from exchange 2016 the default connections are mapi/http this command has been depreciated and hence can skip this step.

So all the outlook clients who are connecting via MAPI post autodiscover request exchange 2016 server accepts them and understands that its is coming from MAPI/HTTP
later it gives the required way to connect for the MAPI clients

2. Point your autodiscover DNS records to the Exchange 2016 server. So for the Exchange 2010 users the connections will be proxied to the Exchange 2010 CAS by the Exchange 2016 CAS service.

3. On your firewall allow connections for both /RPC and /MAPI for Exchange 2010 and 2016 connections. Once the Migration is completed you can remove the /RPC rules from the firewall since all the connections are going to be through MAPI/HTTP .

Few more important Tips:

Outlook 2013 and later all the connections will be established MAPI/HTTP by default and so the connections will be fast.

If the end users are using Outlook 2010 and would need to connect to Exchange 2016 mailboxes they need to have the latest Outlook service Packs installed on their PC.

If you have Outlook 2013 user and wants to connect to the legacy mailbox which resides on the exchange 2010 you can use the below registry key to disable the mapi/http attempt on their PC

HKEYCURRENTUSER- Software – MicrosoftExchange – create a new DWORD  “MapiHttpDisabled” with value 1.

Hope this helps

Thanks 

Sathish Veerapandian

MVP – Exchange