Before you understand the process How to Delete Outlook OST File, you’ll need to know about  Outlook and OST File. Outlook is a popular mail client developed by Microsoft in 1997 used to send and receive mails by accessing Microsoft Exchange Server. In Microsoft Outlook, recipient has option of two different Protocols IMAP(Internet Message Access Protocol) and POP(Post Office Protocol) to receive an email or message. 

Depending upon the protocols, Microsoft Outlook uses OST(Offline Storage Table) and PST(Personal Storage Table) file formats to store and manage different types of data. SMTP(Simple Mail Transfer Protocol) protocol is used at sender side. 

POP is usually known as Post Office Protocol, it is used to store emails from the mail server to the user’s local device in .pst file format. Once downloaded, emails are usually removed from the server. 

The OST file in IMAP serves as a local cache of mailbox data, enabling offline access and Changes made offline are synchronised with the server when a connection is restored. The OST file makes sure you can still check your emails and other stuff even when you’re not connected to the internet which will helps you stay productive and access everything you need, anytime, anywhere.

Important measures to follow before Deleting OST file:- 

How to Backup OST File?

Backing up an OST (Offline Storage Table) file is crucial for safeguarding your email data. Since OST files are essentially local copies of your mailbox data, creating a backup ensures that you can recover your emails and other items in case of unexpected data loss or corruption. Here’s how you can backup an OST file:

Method 1: Use Outlook’s Export Feature or Manually Copy the OST File.

For In-Built Feature:-

1. Open “Outlook”.
2. Click  ‘File’ on the top left corner.
3. Select “Open & Export” option and then choose “Import/Export” .
4. Choose “Export to a file” option and click “Next”.
5. Select “Outlook Data File(.pst)” and click “Next”.
6. Choose the mailbox or Folders you want to export and Ensure that you select the correct OST file you want to backup. If you want to include everything, select your email account at the top level.
7. Specify the destination for the PST file and provide a name for it. 
8. Click “Finish” to start the Export process.

OR

For Manual Process:-

1. Close Outlook to ensure the OST file is not in use.
2. Navigate to the location where the OST file is stored. The default location for OST file is typically:- “ C:\Users\username\AppData\Local\Microsoft\Outlook\ ” .
3. Copy the OST file to a safe location, such as an external hard drive, cloud storage, or another secure location.

Method 2: Use Third Party Backup Tools/Softwares.

You can use third party backup tools available that specialize in backing up Outlook data, including OST files. There are many tools available online that can help you to backup OST files to many different  formats and even convert multiple OST Files into other format at once, which can be further easily accessed. Choose reliable and reputable tool, download and install it on your system where you have access to the OST file.

I have personally used SysTools OST to PST Converter will convert OST Files into Multiple Email Format PST, MBOX, MSG, EML, EMLX, NSF, etc. It helped me to export ost file easily in into Document Format like PDF, vCard, CSV, ICS, TXT, HTML, MHT, DOCX, DOC, RTF, etc.

Steps to Delete Outlook OST File:- 

To delete Outlook OST file , then follow these steps:-

1- Close Outlook: Ensure that Microsoft Outlook is closed to prevent any conflicts while deleting Outlook OST file.

2- Locate OST File: Navigate to the folder where Outlook stores OST files. 

3- Identify OST File: Look for the OST file corresponding to the Outlook profile you wish to delete. The file name usually matches the profile name or contains a unique identifier.

4-Backup OST File (Optional): Before proceeding with deletion, it’s advisable to back up the OST file if you need to preserve any locally cached email data. You can copy the OST file to another location for safekeeping.

5- Delete OST File: Right click on the OST file and select “Delete” from the context menu. Alternatively, you can select the OST file and press the “Delete” key on your keyboard.

6- Confirm Deletion: Windows will prompt you to confirm the deletion of the file. Confirm the action to permanently delete the Outlook OST file.

7- Empty Recycle Bin (Optional): After deleting the Outlook OST file, you can free up disk space by emptying the Recycle Bin. Right click on the “Recycle Bin icon” on your desktop and select “Empty Recycle Bin” to permanently delete the file.

8- Restart Outlook (If Necessary): If you plan to continue using Outlook with the same profile, you can restart the application. Outlook will recreate the OST file the next time you open it and synchronise with the email server.

Deleting Outlook OST file removes the locally cached copy of your mailbox data. However, it does not affect your data on the email server. If you encounter issues with Outlook, deleting the OST file can sometimes resolve synchronisation or corruption problems. 

Why to Delete Outlook OST File:-

Deleting Outlook OST files might be necessary for several reasons:

1- Recovery: If the OST file becomes corrupted or damaged, deleting it can prompt Outlook to recreate a new one, potentially resolving any issues.

2- Space Management: OST files can grow large over time, consuming significant disk space. Deleting them can free up storage space on your computer.

3- Privacy: Deleting Outlook’s OST files can remove cached copies of sensitive or outdated information, enhancing privacy and security.

4- Performance: By Removing the unnecessary OST files can improve Outlook’s performance, especially if they are causing the application to slow down or become unresponsive.