Know How to Increase Outlook File size limit

As an Outlook user you might be familiar with this message  “Mailbox Full: Your mailbox is full, you may not be able to send or receive items” which restricts users to send or receive items. This message generally occurs when  you have consumed your Outlook mailbox to it’s full limit.

If you are encountering mailbox full error which is one of the most common Outlook errors, this article will guide you to increase the .pst and .ost file size limit in various versions of Outlook like Outlook 2019, 2016, 2003, 2007, 2010. So let’s dive deep and get acquainted to the methods using which you can increase the Outlook file size limit.

How to Increase .pst and .ost File Size Limit?

It’s a known fact that in Outlook 2003  and 2007 the maximum limit for .pst and .ost files is set to 20GB but with Outlook 2010 and above that’s not the case as the recommended 

Limit of .pst and .ost file is 50GB. Usually the limit of the files in a program is set by Windows registry, hence the registry value MaxLargeFileSize registry entry is 50 GB while the WarnLargeFileSize registry entry is 47.5GB. However, one can increase the file size limit of PST and OST files using the below mentioned methods.

MaxLargeFileSize value in registry refers to the maximum size limit of .ost and .pst files. Once maximum size limit is reached Outlook does not permit .ost and .pst files to grow further.
While WarnLargeFileSize registry value refers to the maximum data limit. Once the maximum data limit is consumed to its fullest limit, Outlook does not permit it to grow further.

Note: The difference of values between MaxLargeFileSize registry entry of .pst and .ost file and WarnLargeFileSize registry entry should be atleast 5% so that the internal processes are not hindered.

Know How to  Increase Outlook File Size Limit via Registry

Follow the below mentioned steps to increase .pst and .ost file size limit by making changes to registry:

Note: One can use both these methods to increase PST and OST file size limits. The method below is shown for PST format but you can use the same steps to increase OST file size too.

Step 1 : Click on Windows Start button type Run and hit Enter.

Step 2 : Once the Run dialog box appears, type Regedit and click on OK.

Step 3 : Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\PST

Step 4 : Click on PST and  Right-click on it.

 Step 5 : Choose  MaxLargeFileSize from the right pane.

Step 6 : Click on Modify and then type the value.

Step 7:  Click on the OK button. 

Step 8 : Now repeat steps 4 and step 6 by choosing  WarnLargeFileSize as an option.

Note: One has to create MaxLargeFileSize and WarnLargeFileSizeRegistry values if they don’t exist. Follow the below mentioned steps to create registry values.

Step 1 :  Click on Windows Start button type Run and hit Enter.

Step 2 :  Once the Run dialog box appears, type Regedit and click on OK.

Step 3:  Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook 

Step 3 : Right click on Outlook option and go to New option, then select Key.

Step 4 : Now type PST and then hit on Enter.

Step 5 : Right click on PST option and then go to New option.

Step 6 :  Now select DWORD(32-bit) Value option available.

Step 7 : Type MaxLargeFileSize and then hit on ENTER.

Step 8 : Edit DWORD Value window appears. Select the Decimal option and then enter value under the Value data box and then click on the Ok button.

Step 9 : Now, you can go ahead repeating steps 5 and step 7 to create another DWORD(32-bit) Value  for WarnLargeFileSize and then close the registry.

Note: The value to be entered in the Value data box should be either in megabytes or gigabytes. Inorder to enter such values one needs to use a conversion calculator such as Memory and Storage Converter.

When the mailbox is full you might tend to delete mails in-order to make space to send or receive emails. In case some of the mails in your mailbox are missing you can make use of Remo PST Repair Tool to recover crucial Outlook data. It can also help you retrieve severely damaged or corrupt PST files in a few simple clicks.  Download the software now!!

Download Remo Recover for Recycle Bin recovery

Tips to Manage Outlook Efficiently:

  • It is recommended to delete unwanted mails and attachments at regular intervals.
  • Block junk emails like promotional mails which helps to save space.
  • Properly organize your emails into folders at regular intervals.


The above mentioned method can help you to increase PST and OST file size limits. This info will be further updated as and when we encounter any new issues with Outlook in the near future. Suppose if you are encountering problems that are not mentioned above do let us know in the comment section below and let us know if this article was of any help to you or contact our technical support team for any reference.

Know How to Increase Outlook File size limit was last modified: May 11th, 2021 by Tony Landry

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