How to Increase Outlook PST-files and OST-files Mailbox Size Limit-Manual Methods?


This post is dedicated to the users who want to increase the Outlook mailbox size without using any third party application.

Increase MS-Outlook Mailbox Size For PST-files and OST-files

Microsoft Outlook is an excellent email client which proves not only for window’s users but also it works excellently for MAC users. As it is a product of Microsoft then window users generally preferred this tool. So if you are regular users of Outlook you would be aware of the PST file and OST file size limitation, but don’t fret in this situation because we have a solution to come out from this situation, being an MS Outlook users it is very difficult to save the mailbox content into a PST files exceeding from its limit. Actually, PST files size restriction is not the same for every version, it will be different for various version of Outlook.

Let’s have a look on the PST files size limitation for a different version

Various version of Outlook has been launched by Microsoft from 97, 98, 2000, 2002, 2003, 2007, 2010, 2013, and 2016. Although all the data is saved in PST format in Outlook, the size varies from version to version. ANSI (American National Standards Institute) for the version from 2003 to 2016, and it also uses UNICODE which is officially called Unicode Worldwide Character Standard to save PST files. The actual difference between these two standards is the files size limitation, PST files generated in ANSI Code has a size limit of 2GB maximum. Whereas if the OST & PST files saved in UNICODE can store the database 20 GB to 50 GB from Outlook 2003 to 2010, 2013, 2016 and even up to 2019.

Threat with the limitation of OST & PST files

A risk of OST and PST files corruption always there, whenever a PST file reaches its Maximum size limit, the troubles for the Outlook users have started, they can encounter with the poor performance, hard drive crashes issue and hanging issue, and it becomes the serious issue, as these files are prone to corruption and also a risk is there to lose all your important mailbox just because of this corruption issue. The manual tricks to expend the mailbox size limit are listed below. 

Also Read: How to Repair Over-sized PST File Issue in Outlook

You do not need to use any third party tool if you are following these steps, you just need to use Window Registry Editor

  1. Open Window Registry Editor

2. Press Win+R buttons to initiate Run command, type Regedit, and then press Enter.

3. On the left side of the computer screen, you will see a tree-like structure list

Click HKEY_CURRENT_USER to expand the list.

Now search the path to follow a registry according to your Outlook version

For Single users machine

  • HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST for Outlook 2003
  • HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST for Outlook 2007
  • HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST for Outlook 2010
  • HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\PST for Outlook 2013
  • HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST for Outlook 2016
  • HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST for Outlook 2019

For administrators

  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\11.0\Outlook\PST for Outlook 2003
  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Outlook\PST for Outlook 2007
  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\PST for Outlook 2010
  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\PST for Outlook 2013
  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\PST for Outlook 2016
  • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\PST for Outlook 2019

4. Now you will see PST files in the column.

Double click on it and find the two values shown below

  • MaxLargeFileSize
  • WarnLargeFileSize

NOTE:  If these above values are not there then you will have to create them manually.

5. To create MaxLargeFileSize, right-click on the blank space. Click New > DWORD (32-bit) Value.

6. Now write MaxLargeFileSize using your keyboard.

7. Now create WarnLargeFileSize. Right-click on the blank space, New > DWORD (32-bit) Value.

You can now define the data value to each file as you see both of them on the screen.

8. In the list, open MaxLargeFileSize and can define the value in MB.

For example: set the size of the files which is over 20 GB if you are working on Outlook 2003, 2007 or 2010. But if you’re using Outlook 2013 or 2016, then define the size up to 50 GB

Now select the decimal Base from the option. And click OK

9. Now, open the WarnLargeFileSize and define the base value in MB.

10. Now close the Registry Editor

But Remember one thing these manual tricks to expand the Outlook mailbox size PST file & OST File Limit can be used only when you are using UNICODE PST files created by Outlook version 2003 including up to 2019.