Classic Outlook is setup with a 50GB file limit by default. You can increase this limit via the Registry, Group Policies, or using the ZIP file provided below.

The Quick Way – Import A Registry File

We’ve preconfigured a file to set a 100GB limit in outlook. Just download the file below, close all outlook windows, double-click the file and then double click the outlookfix.reg to run it. Approve the Registry Import prompt, then restart your computer and outlook should now run with a 100GB file size limit (warning at 97GB).

NOTE: running files from untrusted sources is dangerous. Please only use this file if you trust us.

Outlookfix.zip

Via the Registry (manual process)

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
  HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST
• Outlook 2007
  HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST
• Outlook 2010
  HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST
• Outlook 2013
  HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\PST
• Outlook 2016 / Outlook 2019 / Outlook 2021 / Outlook 2024 / Microsoft 365
  HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

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. This difference has to be at least 5%.

Note: Although the Registry path says “PST”, it also applies to ost-files.

Via Group Policies

If you are a corporate administrator and want to adjust the maximum allowed sizes of pst-files and ost-files, then you can use Group Policies as well.

The settings for adjusting the maximum file size for pst-files and ost-files can be found in the section;

• User Configuration-> Administrative Templates-> Microsoft Outlook <version>-> Miscellaneous-> PST Settings.

The following 2 settings need to be modified;

• Large PST: Absolute maximum size
  Don’t set this higher than 4294967295
• Large PST: Size to disable adding new content
  Don’t set this higher than 4090445042