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The file size limits of .pst and .ost in Outlook Office 365 ?

Jorge Santistevan 1 Reputation point
2022-03-11T20:17:52.297+00:00

what is the limit of *.ost or *.pst file in outlook in office 365

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Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Kael Yao-MSFT 37,676 Reputation points Microsoft Vendor
    2022-03-14T01:48:54.463+00:00

    Hi @Jorge Santistevan

    Starting from Outlook 2010, in later versions of Outlook (2013/2016/2019/O365) the default file size limit is 50GB.
    Please refer to this link: The file size limits of .pst and .ost files are larger in Outlook 2010 and Outlook 2013
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    3 people found this answer helpful.
  2. Michael Taylor 51,346 Reputation points
    2022-03-11T20:32:40.643+00:00

    Depends upon your subscription and the mailbox. For example a basic MS 365 business account has 50GB of storage for the mailbox and additional storage for archives. Office 365 Ent E3 is 100GB. This is available in the Exchange Online service description.

    If you are a consumer and you're using just Outlook 365 then the limit is documented as being 100GB which coincides with the highest enterprise tier of Exchange. Of course an IT admin can reduce this limit if desired.

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  3. Zenifer Smith 10 Reputation points
    2023-07-28T14:52:37.54+00:00

    In Outlook Office 365, the maximum size limit for .pst and .ost files is 50 GB. PST files can be increased to 100 GB with registry settings, however keeping the files within these limits ensures smooth performance.

    To increase the file size limit for .pst and .ost files in Outlook, you can follow these steps:

    • Close Outlook: Ensure that Outlook is not running before making any changes.
    • Open Registry Editor: Press "Windows + R" to open the Run dialog, type "regedit," and press Enter to open the Registry Editor.
    • Navigate to the Registry Key: In the Registry Editor, navigate to the following key:
    • For .pst files: HKEY_CURRENT_USER\Software\Microsoft\Office{version}\Outlook\PST
    • For .ost files: HKEY_CURRENT_USER\Software\Microsoft\Office{version}\Outlook\OST
    • Note: Replace "{version}" with the appropriate version number (e.g., 16.0 for Outlook 2016, 15.0 for Outlook 2013).
    • Create a New DWORD Value: Right-click on the right-side pane, select "New," and then click "DWORD (32-bit) Value."
    • Name the New Value: Enter "MaxLargeFileSize" as the name of the new DWORD value.
    • Set the Value Data: Double-click on "MaxLargeFileSize," set the "Base" to "Decimal," and enter the desired size limit in megabytes (MB). For example, to set a 100 GB limit, enter "102400."
    • Create Another DWORD Value (optional): If you want to increase the limit for Unicode .pst files (Outlook 2003 and later), create another DWORD value named "MaxLargeFileSizeUnicode" and set the value data as desired.
    • Close Registry Editor: Once you have made the necessary changes, close the Registry Editor.
    • Restart Outlook: After making the changes, restart Outlook for the new file size limit to take effect.
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