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This How.com.vn teaches you how to increase the size of your Microsoft Outlook mailbox by editing the Windows registry. There is no way to increase the mailbox size in Outlook for macOS.

Things You Should Know

  • There is no way to increase the mailbox size in Outlook for macOS.
  • In Windows, edit the registry to increase the size of the Microsoft Outlook mailbox.
  • Press "Win + R" and enter "Regedit" to open the Registry Editor.
  1. How.com.vn English: Step 1 Press ⊞ Win+R.
    This opens the Run tool.
  2. How.com.vn English: Step 2 Type regedit and click OK.
    A confirmation message will appear, asking if you want to allow the app to run.
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  3. How.com.vn English: Step 3 Click Yes.
    The regedit window will appear.
  4. How.com.vn English: Step 4 Double-click HKEY_CURRENT_USER.
    It’s in the left column. Several options will expand below.
  5. How.com.vn English: Step 5 Double-click Software.
    You may have to scroll down a little to see it. A list of software manufacturers will appear.
  6. How.com.vn English: Step 6 Double-click Microsoft.
    A list of Microsoft products will appear in the right column.
  7. How.com.vn English: Step 7 Double-click Office (version).
    Instead of “(version)” you will see the version of Office you’re using (2016, 2013, etc).
  8. How.com.vn English: Step 8 Double-click Outlook.
  9. How.com.vn English: Step 9 Double-click PST.
  10. How.com.vn English: Step 10 Right-click a blank area in the right panel.
    Do this somewhere under the “Default” line that’s at the top of the panel. A context menu will expand.
  11. How.com.vn English: Step 11 Click New.
    Another context menu will expand.
  12. How.com.vn English: Step 12 Click QWORD (64-bit) Value or QWORD (32-bit) Value.
    Select the option that reflects your version of Windows.
  13. How.com.vn English: Step 13 Type MaxLargeFileSize and press ↵ Enter.
    You have now created a registry key called MaxLargeFileSize. Now you’ll create another.
  14. How.com.vn English: Step 14 Right-click the blank area of the panel again.
  15. How.com.vn English: Step 15 Click New.
  16. How.com.vn English: Step 16 Click QWORD (64-bit) Value or QWORD (32-bit) Value.
  17. How.com.vn English: Step 17 Type WarnLargeFileSize and press ↵ Enter.
    This new key will appear below the one you created a moment ago.
  18. How.com.vn English: Step 18 Double-click MaxLargeFileSize.
    A dialog will appear.
  19. How.com.vn English: Step 19 Select Decimal if not already selected.
  20. How.com.vn English: Step 20 Enter the desired size of your mailbox in MB.
    Type it into the “Value data” field.[1]
    • For example, to make your mailbox 75 GB, type 75000 into the box.
    • The default mailbox size for Outlook 2013 or 2016 is 50 GB. The default for Outlook 2003, 2007, and 2010 is 20 GB.
  21. How.com.vn English: Step 21 Click OK.
    Now you’ll do something similar for the next key.
  22. How.com.vn English: Step 22 Double-click WarnLargeFileSize.
  23. How.com.vn English: Step 23 Select Decimal if not already selected.
  24. How.com.vn English: Step 24 Enter the size at which you want to be notified that the mailbox is almost full.
    Again, enter this in MB.
    • For example, if you’ve made your mailbox 75000 MB, you may want Outlook to warn you that you’re nearing the limit at 72000 MB.
  25. How.com.vn English: Step 25 Click OK.
    You have now updated the registry to support a larger mailbox in Outlook.
  26. How.com.vn English: Step 26 Restart your computer.
    Changes to the registry will not take effect until you’ve restarted Windows.
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      About This Article

      How.com.vn English: Nicole Levine, MFA
      Written by:
      How.com.vn Technology Writer
      This article was co-authored by How.com.vn staff writer, Nicole Levine, MFA. Nicole Levine is a Technology Writer and Editor for How.com.vn. She has more than 20 years of experience creating technical documentation and leading support teams at major web hosting and software companies. Nicole also holds an MFA in Creative Writing from Portland State University and teaches composition, fiction-writing, and zine-making at various institutions. This article has been viewed 152,695 times.
      How helpful is this?
      Co-authors: 2
      Updated: July 5, 2023
      Views: 152,695
      Categories: Outlook
      Thanks to all authors for creating a page that has been read 152,695 times.

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