Increase maximum size for pst-files and ost-files

In Outlook 2003 and Outlook 2007, the maximum recommended size of a Unicode pst-file and ost-file has been limited to 20GB.

In Outlook 2010, 2013 and 2016, this recommended limit has been set to 50GB.

You can increase (but also decrease) this limit via the Registry.

To increase the maximum size of pst-files and ost-files in Outlook, you’ll need to create and set 2 values in the following location in the Registry:

  • Outlook 2003
  • Outlook 2007
  • Outlook 2010
  • Outlook 2013
  • Outlook 2016

The following 2 new DWORD values must be created or set;

  • WarnLargeFileSize
    Don’t set this higher than 4090445042 (decimal) or f3cf3cf2 (hexadecimal)
  • MaxLargeFileSize
    Don’t set this higher than 4294967295 (decimal) or ffffffff (hexadecimal)

The first value is how many MB a user can write to a pst-file or ost-file before receiving a warning that the file is full. The second value is how many MB the system can write to a pst-file or ost-file.