Configure the size limit for both (.pst) and (.ost) files in Outlook 2010

By default, the maximum file size of .pst and .ost is 50 GB in Outlook 2010, but we can modify this setting by the following registry entries.

Assuming that Windows Server 2008 or above is the domain controller in the production environment.

Prerequisites
Creating an OU which is named People
Move the user accounts in the People OU

1. At the domain controller, log in as Domain Administrator.
2. Launch "Group Policy Management Console". 
3. Expand "Forest > Domains > <Domain Name> ", right-click "People", select "Create a GPO in this domain, and Link it here".
4. Under "Name", type "Outlook Policy".
5. Click "OK".

Figure 1: Outlook Policy

6. Right-click "Outlook Policy", select "Edit".

7. Expand "User Configuration > Preferences > Windows Settings", right-click "Registry", select "New > Registry Item".

8. Still select "HKEY_CURRENT_USER".

9. Next to "Key Path", type "Software\Microsoft\Office\14.0\Outlook\PST".

10. Next to "Value name", type "MaxLargeFileSize".

11. Next to "Value type", select "REG_DWORD".

12. Next to "Value data", type the value you want.

Figure 2: MaxLargeFileSize properties

13. Click "OK".

14. Close "Group Policy Management Editor".

As a result, the policy is applied to all users.

Remark: For non-domain environment, you have to configure the setting by "Registry Editor".

Remark: You may have to create the registry values if it do not exist in "Registry Editor".

Reference:

The file size limits of .pst and .ost files are larger in Outlook 2010 and Outlook 2013

How to configure the size limit for both (.pst) and (.ost) files in Outlook

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