The file size limits of .pst and .ost files are larger in Outlook 2010
By default, Personal Folders (.pst) and Offline Store (.ost) files are in Unicode format in Microsoft Outlook 2010. The overall size of .pst and .ost files have a pre-configured limit of 50 GB. This limit is larger than the current limit for Unicode .pst and .ost files in Microsoft Office Outlook 2007 and in Outlook 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
) The .pst file has a different format and folder size limit in Outlook 2007 and in Outlook 2003
Note The Outlook 2010 file size limit of 50 GB can be increased or decreased by making changes to the Windows registry. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
) How to configure the size limit for both (.pst) and (.ost) files in Outlook 2007 and in Outlook 2003
The default .pst file size limit in Outlook 2007 and in Outlook 2003 is 20 GB. If you want to access a Unicode .pst file that was created in Outlook 2010 on a different computer that has Outlook 2007 or Outlook 2003 installed, you may have to reduce the size of the .pst file if the current file size is at or near 20 GB. If the file size is greater than 20 GB, you will be unable to open the Outlook 2010.pst file.