How to resolve Oversized OST and PST Problem in Outlook

OST (Offline Storage Table) stores the Outlook Mails, Calendars, Tasks and other items as a replica for offline use. When Microsoft Outlook is configured with Exchange Server using Cache Exchange Mode, OST file are created. Just like PST (Personal Storage Table), OST files are stored on a local computer (i.e. client system). Microsoft Outlook 2002 and previous versions Outlook limits the OST file size up to 2 GB maximum. If the OST file becomes oversized (i.e. crossed 2 GB limitation) then it will become unusable, and the user get the following error message:

Errors have been detected in the file Quit all mail-enabled applications, and then use the Inbox Repair Tool.

Oversized Problem of OST files

The maximum limit of OST file for various Outlook editions are:

• Outlook 2002 and Previous Editions of Outlook: 2 GB
• Outlook 2003 and 2007 Edition: 20 GB
• Outlook 2010 and 2013: 50 GB 

The 2 GB file limit was in an earlier edition of Microsoft Outlook, which causes the problem as the data size grows abnormally. The reason behind this is because of ANSI format of Outlook Data Files (both for OST and PST). With the release of Outlook 2003 Edition, Microsoft Outlook was started using UNICODE file format for OST and PST files. The main advantage of UNICODE over ANSI format is that it supports multi-character encoding (using 32 bit with UTF-32 encoding). 

Top 3 Methods to Repair Oversized OST [Step By Step Guide] 

When OST files become oversized, it is unusable, and the user cannot access his/her emails. To avoid this limitation you can change the oversized limit by registry tweek. 

Method #1 Change Outlook Data File (OST and PST)Size Limit using Registry Settings 

The size limit can be changed by changing the following registry keys:

• The MaxFileSize registry entry
• The WarnFileSize registry entry
• The MaxLargeFileSize registry entry
• The WarnLargeFileSize registry entry

You can read this Microsoft KB Document in order to configure the size limit for outlook data files (.pst and .ost). 

Method #2 Use Microsoft OST and PST Crop Tool  

For oversized OST, the Microsoft Inbox Repair Tools fails to repair the OST file but you can try PST2GB CROP Tool from Microsoft which is freely available. 

Limitation: The tool Simply deletes the oversized data from your PST or OST file. So, It will cause loss of email data.

Method #3 Use OST Converter Tool and Split Oversized Files

If you can not afford to loose your important emails (deleted by PST2GB Tool from Microsoft), then it is better to choose OST Converter Tool which can convert OST file of any size (no 2 GB size limitations) and also you can split the files according to your desired file size. 

Free Download Link: http://www.pcvita.com/ost-converter.html