CPU usage is high when you use RPC over HTTP protocol in Windows 8.1 or Windows Server 2012 R2

Consider the following scenario that takes 2013 as an example:

  • The Mailbox server role is enabled in .
  • Exchange mailboxes use extended MAPI to communicate with the Exchange Server.
  • The extended MAPI uses Microsoft over (remote procedure call over ) protocol.
  • Many clients (such as devices) are dropping connections to the Exchange Server.

In this scenario, the CPU usage on the Exchange server may reach 100 percent.\

Hotfix: https://support.microsoft.com/en-us/hotfix/kbhotfix?kbnum=3041832&kbln=en-US