Consider the following scenario that takes Microsoft Exchange Server 2013 as an example:
- The Mailbox server role is enabled in Exchange Server 2013.
- Exchange mailboxes use extended MAPI to communicate with the Exchange Server.
- The extended MAPI uses Microsoft RPC over HTTP (remote procedure call over HTTP) protocol.
- Many clients (such as mobile devices) are dropping connections to the Exchange Server.
In this scenario, the CPU usage on the Exchange server may reach 100 percent.\
Action Required by: October 31, 2017 at 5:59 PM UTC
Details: On October 31st, 2017, Exchange Online mailboxes in Office 365 will require connections from Outlook for Windows use MAPI over HTTP, our new method of connectivity and transport between Outlook for Windows and Exchange. In May of 2014, Microsoft introduced MAPI over HTTP as a replacement for RPC over HTTP. RPC over HTTP was a legacy connection protocol that is being deprecated from Exchange Online. Beginning October 31, 2017, Outlook for Windows clients using RPC over HTTP will be unable to access their Exchange Online mailbox. The necessary action depends on the version of Outlook in use in your organization. If you are using Outlook 2007 or earlier, you need to upgrade. Outlook 2007 does not contain support for the MAPI/HTTP protocol. We encourage you to update to the Office 365 ProPlus subscription, or access Outlook via the web browser (which is included in your current subscription plan). Outlook 2010-2016 customers will need to ensure their version of Outlook for Windows is set up to support MAPI/HTTP. At a minimum, you should ensure you have installed the December 2015 update. Lastly, ensure your Outlook clients are not using a registry key to block MAPI/HTTP.
Message Center: MC85988 – Potential service disruption for Outlook for Windows users
Posted: November 16, 2016
Additional Information: KB3201590: RPC over HTTP deprecated in Office 365 on October 31, 2017