Tuesday, September 2, 2014

Defining MS Outlook Connectivity with MAPI over HTTP Protocol

MAPI Over HTTP Introduced: Outlook Connectivity Transport Improves

Exchange 2013 Service Pack1 came with a set of new features recently, including the support for MAPI over HTTP. Messaging API over HTTP is the new kind of transport protocol introduced in the Microsoft Outlook and Exchange Server SP1 respectively. This newly implemented protocol to the MS Outlook & Exchange connection adds an additional level of improvement to the stability and reliability to it simply by advancing the transport layer to an industry standard of HTTP pattern.

“The protocol is a long-run alternative to the RPC/HTTP connection which was commonly known as the Outlook Anywhere service.”

The introduction of this transport protocol also resulted in the removal of complications that were associated with the dependency of Outlook Anywhere with the inherited RPC technology. (The Remote Procedure Call / HTTP is a protocol that permits an internet based client to establish secure connection with MS Exchange Server without the prior login into a VPN being required.)

Mainly, this permits a greater level of visibility & enhanced ability to recover the transfer related errors. An additional function that is provided along with, is the support for pause & resume which further allows clients supported, to switch networks or resuming from the state of hibernation while the same server context is being maintained.

NOTE: However, implementing MAPI/HTTP doesn’t necessarily mean that it is the only protocol that now remains to be used for MS Outlook to acquiring access of Exchange. Those Outlook clients which are still not MAPI/HTTP enabled or capable can certainly make use of Outlook Anywhere i.e. RPC/HTTP for gaining access to Exchange via a MAPI supported client access server.

TIP: In order to avoid performance related issues from being surfaced, users accessing Exchange using MAPI over HTTP protocol are advised to either upgrade from Exchange 2013 RTM or completely install the new Exchange Server 2013 SP1.

MAPI Over HTTP – The Architecture

The images displayed below will help offer a well-defined visual demonstration on the architectural difference between Outlook Anywhere & the latest; MAPI/HTTP transport protocol.


As you can clearly observe in the images displayed above that with the new feature in Exchange, there is no need of opening the prolonged TCP based connections now. The twin, data in and out connections that were needed in the past for each session of the RPC/HTTP are also not required anymore.

Benefits Gained: This helps in the reduction of simultaneously running TCP connections set up amongst the client & server. MAPI/HTTP, on the other hand, will only produce two simultaneous connections at a time, resulting in the generation of one long lived & one short lived additional connection respectively.

Some Of The Major Differences Detected

  1. Reduced Consumption of Time & Expenses: MAPI/HTTP separates a session between the client & a server from the basic network connection. Meanwhile, the entire session would be invalidated and would have to be reestablished from the start if connectivity with the network was somehow lost from between the server and client in case of Outlook Anywhere.
  2. Helping Low Quality Network Users: When using MAPI/HTTP, if a loss of network connection is encountered, the session does not restart until the next 15 minutes, offering the client with the freedom of just reconnecting as soon as the connection is reestablished and continue right from the point where it last left off at the time the interruption that took place.

  3. Network Blip Consequences Avoided: Earlier, just a single unanticipated server-side blip of the network would result in the invalidation of all client sessions that later leads to a rush of reconnections being made to mailbox server. This turned out as a huge culprit behind the straining of mailbox server resources in the process of reestablishing multiple number of RPC/HTTP connections at once. The discussed scenario is now avoided with the MAPI/HTTP feature being introduced.

What Induced The Origination Of MAPI/HTTP?

Quite obviously, the original infrastructure of Outlook Anywhere that came out with Exchange 2003 wasn’t made to suit the client connections currently being made from a far too large variation of network types.

There are now home based networks, cellular networks and even in-flight wireless networks, which are enough to describe the diversity present today in the types of network connections than there were before.

The primary motive of the Microsoft Team to come up with the MAPI/HTTP feature was not only to meet the needs of users making client connections using such diverse network types. But, they also wanted to make the infrastructure more simplified than it was when only RPC/HTTP existed. Some more motives associated with the MAPI/HTTP feature:

  • To provide an improved user experience for all types of network connections with faster connection to Exchange.
  • To ameliorate the connection resilience in case, packets are dropped in transit by the network.
The final result of the in-house user testing executed by Microsoft that will help quantify the improvements made in the architecture of Outlook Anywhere via MAPI/HTTP:
  1. Improvements On The User End: The ‘Connecting to Outlook’ welcome message which used to be displayed earlier has been omitted from the scene. Resultantly, the same Outlook launch & synchronization, which earlier took 90 seconds was further amended and reduced to as low as 30 seconds that was reportedly monitored in 70% of the clients.
In addition to that, improvements were also observed while resuming Outlook from a hibernated state or when reconnected to a different/new network.
The results of the in-house testing by Microsoft showed that a total of 80% clients that used MAPI over HTTP began syncing within 30 seconds versus more than 40 seconds of time taken by Outlook Anywhere clients while resuming from a hibernated state.
The tested improvement was possible because MAPI over HTTP comes with a pause & resume facility that enables clients to resume the use of an available network connection instead of managing with a new connection every time.
Start Sync

NOTE: The current sessions of MAPI over HTTP remain valid for 15 minutes. However, if this duration is fine-tuned & expanded, the improvements will become more noticeable.
  1. Improvements For Administrators (IT): Not only do the end users get benefitted with this new addition to the Exchange 2013. But even the IT administrators will be able to attain protocol visibility at a greater level that will allow them to distinguish and rectify situations more quickly and confidently.
As MAPI/HTTP moves to a traditional protocol payload of HTTP, it becomes possible to use the known tools familiar to HTTP debugging. Now it will become possible for IIS & HTTPProxy logs to contain information matching other HTTP based protocols such as; OWA (Outlook Web App) and pass on information through headers.
This move will put all customers on an equal level playing field for the tools available for debugging purposes as, previously some RPC/HTTP debug procedures were only usable via trademarked Microsoft Tools only.
  1. Improvements For Administrators (Exchange): Exchange Administrators will be able to observe that the response reverted by Autodiscover for MAPI over HTTP with Outlook will be greatly simplified. The settings that are returned are basically depicted the protocol edition and endpoint URLs for Outlook to be able to establish connection with Exchange mailbox along with directory from both; inside or outside a customer’s business network.
Outlook handles the URLs returned as unclear and uses as-is which in turn minimizes the chances of connection breaking with the future changes in the endpoint. As MAPI over HTTP like any web protocol just sends an unidentified HTTP request to Exchange to get back authentication settings; there is basically no requirement for Autodiscover to promote the authentication settings making it easier for rolling out modifications to the Outlook authentication settings.
How Does MAPI Over HTTP Functions?
Following is a supposed scenario of:
  1. An Outlook 2013 SP1 Client
  2. Connecting to Exchange Server 2013 SP1
  3. After enabling MAPI over HTTP
The stages:
  1. The Outlook client starts up with an Autodiscover POST request displayed. In the request it has included a new concept that promotes; the client is MAPI over HTTP capable with the attribute X-MapiHTTPCapability = 1. 
  1. Exchange Server observes that the request has been received from a MAPI over HTTP enabled client and answers with the respective MAPI/HTTP information with the settings on how to connect to a mailbox working on MAPI over HTTP, included. This takes on that the MAPI/HTTP is configured and is also enabled on the respective server.
  2. Outlook detects the new connection path and reminds the user to restart their Outlook to switch to the new connection. Outlook will continue to use the services of Outlook Anywhere until the restart remains pending. NOTE: We suggest that you set up the latest updates of the Office client to provide the best user experience. Once the updates are done the prompt is removed and clients are then allowed to make transitions when the next unprompted Outlook restart takes place.
    Quit & Restart Outlook
  1. Once Outlook restarts, it then starts using MAPI/HTTP to carry out communication with Exchange.
What Does The Future Hold?
With MAPI over HTTP, the Exchange team comes under the position of innovating quickly. It has simplified the entire architecture by removing dependency on RPC technology which is no longer evolving as quickly as the customer needs are. An extensibility of the connection abilities is provided with this change.
The Microsoft Team is working on a new capability which is in the direction of Outlook to enable multiple factor authentications for Office365 users. MAPI/HTTP makes this capability possible and is planned to be delivered to the end users by the end of this year.
Prerequisites Of Owning MAPI/HTTP

For those, who have clearly decided upon benefitting themselves with the associated benefits of MAPI/HTTP can enable it by following the below mentioned prerequisites.

Server Based Requirements: To make use of the MAPI over HTTP you are required to update all Exchange 2013 Client Access Servers to Exchange Server 2013 SP1 or later. The feature comes disabled in the Service Pack1 by default, so you can easily get the servers updated and no one will notice the changes. Meanwhile, the Office 365 Exchange Online users have nothing to worry about in the context of the server side of deployment.

Client Based Requirements: All Outlook clients should be updated to MAPI/HTTP usage. Office 2013 Service Pack1 or Office 365 ProPlus February month of update (SP1 is equivalent for ProPlus) are necessary for MAPI/HTTP. It is strictly recommended that you deploy the Office 2013 public update of the month of May or Office 365 ProPlus update of the month of April, to avoid the restart reminded as soon as MAPI over HTTP gets enabled for your users.
NOTE: Older versions of the client will continue working as-is with Outlook Anywhere. The service works as the supported connection procedure for those clients. However, in a future update, Microsoft plans to add up the MAPI/HTTP support to Outlook 2010, which will be announced when its availability will be possible.

In the end, updating from the outdated to the updated is always a good choice to make, especially when the ratio is; no benefits to advanced benefits. Pros and cons along with each of the necessary details have been mentioned in the article above. However, there are no as such drawbacks of enabling MAPI/HTTP as you will still be provided with the option to continue using RPC over HTTP.


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