This post is also available in: Polish
If you use Outlook with internet mailbox or with Exchange cached mode, outlook will use .pst or .ost file to store data.
Each of this files has his own maximum data limit supported by Outlook.
If this limit is reached .pst or .ost files are permitted to add any more data.
If outlook pst, ost file reach the size limit then you will get the warning.
Below, in table you can check maximum size limit, depended on Outlook version.
Outlook 2010
| Name | Type | Valid Data Range | Default |
| MaxLargeFileSize | REG_DWORD | 0x00000001 – 0x0000C800 | 0x0000C800 51,200 (50 GB) |
| WarnLargeFileSize | REG_DWORD | 0x00000000 – 0x0000BE00 | 0x0000BE00 48,640 (47.5 GB) |
| MaxFileSize | REG_DWORD | 0x001F4400 – 0x7C004400 | 0x7BB04400 2,075,149,312 (1.933 GB) |
| WarnFileSize | REG_DWORD | 0x00042400 – 0x7C004400 | 0x74404400 1,950,368,768 (1.816 GB) |
Outlook 2007 and Outlook 2003
| Name | Type | Valid Data Range | Default |
| MaxLargeFileSize | REG_DWORD | 0x00000001 – 0x0000C800 | 0x00005000 20,480 (20 GB) |
| WarnLargeFileSize | REG_DWORD | 0x00000000 – 0x0000BE00 | 0x00004C00 19,456 (19 GB) |
| MaxFileSize | REG_DWORD | 0x001F4400 – 0x7C004400 | 0x7BB04400 2,075,149,312 (1.933 GB) |
| WarnFileSize | REG_DWORD | 0x00042400 – 0x7C004400 | 0x74404400 1,950,368,768 (1.816 GB) |
You can use the registry to set the size limit for the pst ost files.
To change this settings, you have to modify registry values:
- MaxFileSize registry entry
- WarnFileSize registry entry
- MaxLargeFileSize registry entry
- WarnLargeFileSize registry entry
Open Regedit and go to location in registry depending on Outlook version:
Outlook 2010
The policy location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\PST
The user preference location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST
Outlook 2007
The policy location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Outlook\PST
The user preference location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST
Outlook 2003
The policy location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\11.0\Outlook\PST
The user preference location for the registry entries is located in the following path in Registry Editor:
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST
English 
polski