STEP 1: Open & Launch the OST Recovery Tool. Click Start » Search OST Recovery Tool » Launch SysTools OST Recovery Software
STEP 2: To select the OST file, click on "ADD File" button as highlighted below.
STEP 3: As you click on Add file button, a small window will pop up and you need to browse the OST file location from machine.
STEP 4: Select any one of the OST files from the folder. The size of OST file has no limitation as you can see in image that the selected OST file is quite large in size
STEP 5: After adding the OST file
Advance Scan Option: This option is workable if your OST file is severely corrupt or auto scanning fails to recover OST file data.
STEP 6: The following screen will appear complete ost file data to export into...
STEP 7: The following Export option window will pop up. Here you can choose the appropriate file format, filter mail and define a size to split PST file.
STEP 8: Save setting to split size of pst file.
STEP 9: You have several option to export ost file...
STEP 10: Export process complete.