OST file is a variant of PST file in Windows Outlook but serves a slightly different purpose and works slightly differently. It is now used automatically by Outlook 2016 and later versions to be used with all Exchange, Outlook.com, and IMAP accounts as well if you are using the offline cached mode.
Basically, all the data from servers are downloaded to the local OST file in your computer (or all the data that you specify while adding the account). This allows users to work seamlessly in Outlook and the downloaded emails even in an offline mode.
Issues with Large OST files in Windows
But there’s an issue. While the older versions of Outlook, the ones using PST format by default, allow a simple way to change the default location for the PST file, it is not possible to simply change the default location for OST file. It will automatically be saved inside the Profile directory for the account associated with it. When you download a lot of emails, this OST file can get very large and may start to cause issues. When such data files become too massive to handle by the disk it is stored in, you start seeing performance issues and even errors. At such times, it makes sense to move the file to another drive in your PC that has the space required to store it.
But changing the location for OST file is slightly tricky. Some will suggest making changes to the registry settings in Windows, however, we do not recommend it. It is a bit risky to make changes through registry, as Windows Outlook does not natively support changing the location for OST file.
The good news is, there is a small trick that you can use to achieve the same effect. In short, Windows Outlook will still consider the location the same as default, but you can change it physically to anywhere else. This is done through a Windows feature called “Symbolic Link.”
How to Change OST file Location in Windows Outlook using “Symbolic Links”
Although, symbolic links are often used in a more advanced IT challenges, but one of its uses can simply be applied for our purpose without altering much of anything.
Symbolic links mean creating a link for a folder or a file to another location. This may sound just like a shortcut in Windows, and it pretty much is for our purpose, but it is created “symbolically.” Simply put – the application will deal with the OST file from its default location the same way as it generally does, however, it will do so with the symbolic link and the actual file will be moved to another location.
Outlook will access the file in the usual fashion, but Windows will automatically redirect it to the new location of the OST file without affecting Outlook at all or its functions with the OST format. The best part is that it remains transparent and hidden. Note that there are two kinds of links: soft and hard links. For our purpose, you need to create a soft or a symbolic link.
Here’s how to create the symbolic link for your OST file:
- Move the OST file manually to the location you want. Copy and Paste and then delete the original file (or keep it as a backup somewhere else just in case something goes wrong).
- Open command prompt in administrator mode. Click “Start” button, type CMD, right-click the command prompt and choose “open as administrator”
- Type the following code: “mklink link target”
Where ‘link’ is the location of your original file and ‘target’ is where you want to keep it (where you moved the file in the first step)
- Press “Enter” in the command prompt and close it.
This will create the symbolic link for the OST file. You can still see the file inside the Outlook profile in the original location, but it will just be a link pointing to the new location. Symbolic links do not have any sort of symbol or sign to identify them as links. They just look like the normal files. But in reality, they do not exit and take up no space in your drive.
To undo the symbolic link, delete the “link” and then move the file back to its original location. This will automatically delete the symbolic link created in command prompt. Hope this helps you in moving the OST file in Windows Outlook. IT’s a much easier and safer way than doing so through registry.