How to Increase Mailbox Size in Outlook

  • To increase Mailbox Size in Outlook. Go to Run>type regedit>HKEY_CURRENT_USER>Find PST location.
  • Click on the Blank Space>New>Dword(32bit or 64bit).
  • Create a value with name MaxLargeFileSize and other one WarnLargeFileSize.
  • Close the Registry Editor.

Summary: If you find yourself in trouble while using Outlook, don’t worry. There are a few ways to increase mailbox size in Outlook so that you can continue using Outlook without any problems.

If you’re using Outlook 2016, you may have noticed that your mailbox size is gradually increasing over time. It is because Outlook stores more and more data in your mailbox as you use it, including emails, attachments, contacts, and calendar entries. While this can be convenient, it can also lead to your mailbox becoming full and preventing you from sending or receiving new emails. So, it’s very important for every user to increase mailbox size in Outlook. Without this, their application won’t work properly.

There is no denying the fact that the PST file size limitation varies from version to version. In Outlook 2002, the maximum file size is only 2 GB, whereas the PST file size is 50 GB in Outlook 2016. So you can save more data in the latest versions.

However, after reaching the size limit, you turn to the error of Outlook mailbox size limit exceeded. But there are some ways by which you can increase mailbox size in Outlook.

Reasons Behind of Outlook Mailbox Size Limit Exceeded

  • Outlook runs on the Exchange server, and your mailbox has its maximum size limit.
  • You are using an older version of the Office data file (.ost or .pst).
  • PST file exceeds the default size of Outlook.

Also Read: Rules Not Working in Outlook

Manual Way For Outlook Increase Mailbox Size From Registry

If the size of Outlook mailbox is full, you can increase your mailbox size by following the manual process below. It is a free way to resolve the issue.

Step 1: Press the Win + R keys together to open the Run command.

Step 2: In the run command box, type regedit, and then click OK.

increase mailbox size using regedit command

Step 3: Here, the Registry Editor opens and displays on your computer screen.

Step 4: Expand the HKEY_CURRENT_USER option from the list on the left side of the window.

increase outlook mailbox size with Hkey current user

Find the PST file using the below path.

  • Single Users can use these paths according to Outlook versions.

For Outlook 2003


For Outlook 2007


For Outlook 2010


For Outlook 2013


For Outlook 2016


  • For the Administrator accounts can use these paths according to Outlook versions.

For Outlook 2003


For Outlook 2007


For Outlook 2010


For Outlook 2013


For Outlook 2016


Step 5: If these values are unavailable, you should create the two values first.

  • MaxlargeFileSize
  • WarnLargeFileSize

Step 6: Right-click on the blank space in the dialog box.

Step 7: Click on the New option and then choose the DWORD (32-bit) Value (or, if you are on a 64-bit operating system, determine QWORD (64-bit) Value).

outlook mailbox size increase 64 bit value

Step 8: Provide the name of the entry, such as MaxLargeFileSize.

Step 9: Repeat the Step 8 process to create a new value and provide a name for this entry as WarnLargeFileSize.

outlook increase mailbox size

Step 10: Double-click on the MaxLargeFileSize and provide a value to the entries.

Step 11: In the Value Size field, enter the maximum size of the PST file in MB.

Step 12: For Outlook 2016, the size limit is 50 GB. Therefore, you can enter 102400 for 100 GB. Choose Decimal in the Base and click Ok to save it.

Step 13: Double-click WarnLargeFileSize and enter 95% of the MaxLargeFileSize value. Select the Base as Decimal again and click the OK button.

Step 14: Finally, close the Registry Editor window.

Step 15: Now, check the mailbox size in Outlook has increased.

Also Read: Emails stuck in Outbox of Outlook

How to Check Outlook Mailbox Size Limit

  1. Click on your account under the Mail view.
  2. Now, click on the Folder menu, then select Folder Properties.
  3. Press on the Folder Size from the display window.
  4. You’ll see that the disk space for the mailbox and each subfolder is indicated in kilobytes (KB).


In conclusion, if you are facing problems while increase mailbox size in Outlook, there are some methods you can try. One method is to use the Properties dialog box to set mailbox size limits. Another way to increase your mailbox size is by adjusting server settings.

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