Configure File Size Limit in Outlook 2003 for PST and OST

Aftab Alam | Updated On - 24 Feb 2021 |

Read time 3 min

If you want to configure file size limit of PST and OST files in MS Outlook 2003, then this article would be helpful a lot. Microsoft Office Outlook 2003 supports both ANSI and UNICODE personal folders .PST and offline folder .OST files. Using the below mentioned registry entries will help in limiting the size of both PST and OST files.

  • MaxFileSize registry entry – It determines the absolute maximum size that both PST and OST files can grow to. After this maximum size is reached, Outlook does not permit the size of the file to grow beyond this size.
  • WarnFileSize registry entry – it determines the maximum data that both the PST and OST files can contain. After this maximum data is reached, neither PST nor OST files are permitted to add any more data.

Location for these registry entries is located in following path in Registry Editor:


Continuing with configuration of file size limit, it should be noted that serious problems tend to occur if you modify the registry incorrectly. Follow these steps to configure the size limit for both the .pst and the .ost files

  1. Click Start , and then click Run.
  2. Type Regedit , and then click OK.
  3. In the left pane, expand My Computer , and then expand HKEY_CURRENT_USER.
  4. Expand Software, and then expand Policies .
  5. Expand Microsoft , and then expand Office.
  6. Expand 11.0 for Outlook 2003 and then expand Outlook .
  7. Click PST, and then right-click MaxFileSize in the right pane.
  8. Click Modify, and then type the value in the Value data box.
  9. Click OK.
  10. Right-click WarnFileSize, and repeat steps 8 through 9.
  11. Right-click MaxLargeFileSize, and repeat steps 8 through 9.
  12. Right-click WarnLargeFileSize, and repeat steps 8 through 9.

This way user can configure the file size limit of PST as well as OST file in Outlook 2003.

Whenever MaxFileSize registry entry value exceeds the ANSI 2 gigabyte (GB) limit on either the PST or OST files, the value is ignored to limit the size to 2 GB to prevent corruption. The default value for the WarnFileSizeregistry registry entry is calculated to be 95% of the MaxFileSize registry entry for a UNICODE file. It is to be noted that when WarnFileSize or WarnLargeFileSize limit is reached, e-mail messages cannot be sent, and items cannot be copied or moved within the file.


When the PST file size increases, Outlook will first notify you about the increased size. After reaching the size limit, it will stop the user account from sending or receiving the emails. Although you can change the PST file size by altering the registry setting values, they are not feasible to maintain safely. Outlook will become slower, and the mailbox will find it hard to run a proper email communication.

PST files may also become corrupt, or data get lost due to improper management. To reduce such problems, you can use the Kernel PST Repair tool to repair the corrupt files and save them again. It will also divide a large PST file into several smaller PST files to reduce the burden on Outlook. Later, you can include all these PST files in Outlook and access the mailbox data.