Occasionally discovery of PST-based source data will fail.  This is frequently caused by PST files which are in an inconsistent and/or corrupt state.  An example error seen in the logs is

Error 15003 when processing PST files
 

This normally maps to MAPI error 0x80040600. 0x80040600 means MAPI_E_CORRUPT_STORE. This generally means that the PST file is corrupt.

ScanPST can sometimes repair it. If however you are crawling over a network share, then the profile might get corrupt if there are any glitches on the network, and that will produce the same error code, even though the file isn't corrupt. So either the PST file itself is indeed corrupt, or there was some unexpected profile corruption when trying to access that file.

ScanPST is a free utility from Microsoft designed to repair corrupt or damaged Outlook PST files. The Inbox Repair tool (Scanpst.exe) is designed to help repair problems that are associated with personal folder (.pst) files.

How to Fix Corrupt PST Using ScanPST.exe and Running Email File Integrity for Processing

 1. Copy the corrupt PST from the source and save locally to your machine.

2. Open ScanPST (typically located in one of the following folders)
a. C:\Program Files\Common Files\System\Mapi\1033\ (Outlook 2003)
b. C:\Program Files\Common Files\System\MSMAPI\1033 (Outlook 2003)
c. C:\Program Files\Microsoft Office\Office12 (Outlook 2007)
d. C:\Program Files\Microsoft Office\Office14 (Outlook 2010)
 

3.To run the Inbox Repair Tool, follow these steps:
a. Click Start, and then point to Find or to Search, depending upon your operating system.
b. In the Search for files or folders named box, type scanpst.exe
c. Double click the Scanpst.exe file to open the Inbox Repair Tool.
d. Type the path and the file name of the personal folders (.pst) file or click Browse to locate the file by using the Windows file system.
e. Click Start. Run multiple times until error count is zero.
f.  Copy the fixed PST back to source and append “_fixed” to file name for distinction.
 

From Clearwell, go to Case Sources, check\select the fixed PST and Perform action: ‘Check Email File Integrity’.

Re-running discovery of this specific source should now be successful.