How to Increase maximum size for Office 365 .PST and .OST files from 50GB to 100GB

 

In Outlook 2010, 2013, 2016, 2019 and Microsoft 365, this recommended  limit has been set to 50GB.

In this example the maximum size of pst-files and ost-files has been set to 100GB with a warning at 95GB.

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

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
  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 / 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% since there is more written to a pst-file and ost-file than just user data.