MapiExceptionTimeout errors are thrown unexpectedly when you use the managed folder assistant with large-scale public folder hierarchies in a Microsoft Exchange Server 2013 environment.
This issue occurs because of the MapiTimeOut exceptions that occur when the managed folder assistant performs some maintenance activities in Public folder mailboxes.
To resolve this issue, install Cumulative Update 9 for Exchange Server 2013.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the managed folder assistant, see Configure the Managed Folder Assistant.