How to Enlarge Microsoft Outlook Mailbox Size

In this article, we are going to plug the issue of the size of your Microsoft Outlook mailbox through modifying the Windows registry. Although there is no other way round to increase the size in Outlook mailbox for macOS, it can happen in PC or Mac. Here we go, in the following simple steps as are:


  1. Tap “Window key+R” for opening the Run tool.
  2. Write “regedit” and press “OK”, and then a confirmation text will appear to inquire to allowing the app to run.
  3. Press “Yes” and then regedit window will be opened.
  4. Double-tap “HKEY_CURRENT_USER”, present in the left column, then various options will be opened below.
  5. Double-tap “Software” under the list of expanded options, then a series of software manufacturers will be catalogued.
  6. Double-tap “Microsoft” then Microsoft products will be enlisted in the right column.
  7. Double-tap “Office (version)”. Rather than “(version)”you will observe the version of Office you are running (2013, 2016 etc.).
  8. Double-tap “Outlook” under the expanded list.
  9. Double-tap “PST” within “Outlook”.
  10. Right-press a blank area visible in the right panel, then a context menu will expand.
  11. Press “New” then another context menu will open.
  12. Press “QWORD (64-bit) Value” or “QWORD (32-bit) Value” after choosing the button that shows your windows version.
  13. Write “MaxLargeFileSize” and click “Enter”. Now, you have made a registry key named as “MaxLargeFileSize”, and it’s time to create another one.
  14. Right-press a blank area of the panel again, then press “New”. Press “QWORD (64-bit) Value” or “QWORD (32-bit) Value depends on your system, then put “WarnLargeFileSize”, and click “Enter”. Now, your other new registry key is created.
  15. Double-tap “MaxLargeFileSize”, then dialogue will open.
  16. Choose “Decimal”, if not already chosen. Insert the desired size in MB for your Outlook mailbox. Write it into the “Value data” box.
  17. Press “OK”. Now you can do the same for the next registry key. Double-tap “WarnLargeFileSize”. Choose “Decimal”, if not already chosen.
  18. Insert the size in MB that you desire to be notified when the mailbox is almost full.
  19. Press “OK”. Now you have updated the registry for assisting a larger Outlook mailbox.
  20. Alterations to the registry will not come into effect forthwith. To do the changes successfully, you have to “Restart” your PC or Mac.

Olivia Jones is a self-professed security expert; she has been making the people aware of the security threats.Her passion is to write about Cyber security, cryptography, malware, social engineering, internet and new media. He writes for Norton security products at


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