Issue
The following may be logged in the Exchange Import module log file:

2013-12-19 18:23:47Z|ERROR|P:7612|T:42|MAPIWrapper|Ingestion to Mailbox failed
EXCEPTION: System.Runtime.InteropServices.COMException (0x80040305): Error in IMAPIFolder.CreateMessage: MAPI_E_TOO_BIG
ulVersion: 0
Error: Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing.
Component: Microsoft Exchange Information Store
ulLowLevelError: 1246
ulContext: 1354
   at Interop.Redemption.RDOItemsClass.Add(Object Type)
   at ArchiveShuttle.Modules.ExchangeLibrary.MAPIWrapper.IngestMSGFile(IRDOFolder2 mapiFolder, FileInfo msgFileFullPath)

Solution
Exchange 2010 and higher have a number of mechanisms to prevent mis-use of per-user limits. These are described in the following article:
http://technet.microsoft.com/en-us/library/ff477612(v=exchg.141).aspx#OIL
The article also explains how to raise these limits. It is necessary to raise the limits in order for a service account to operate successfully.

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