3 Easy Ways to Backup OST File in Outlook

You will learn what OST is in Outlook, the difference between OST and OST files, and 3 simple ways to backup OST file in Outlook easily here.


By Jonna Updated on October 20, 2023

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What is OST File in Outlook?

Microsoft Outlook is a favored email client designed to manage email communication through Microsoft Exchange Server. An OST file (stands for Offline Storage Table) is an offline folder file in Microsoft Outlook. This file makes it possible for users to work offline and synchronize changes with Exchange server when they connect to the network the next time. The ability to work offline proves particularly useful in environments with limited or unreliable internet connectivity.

OST files typically include a range of data and account information such as calendar data, contacts, email messages, tasks, and more. C:\Users\user\AppData\Local\Microsoft\Outlook is the common Outlook OST file location on Windows 10/11. Undoubtedly, OST files are important. So here comes the question: Is it necessary to backup OST file in Outlook? How to backup it? Please keep reading!

Backup OST File Outlook

Do I Need to Backup Outlook OST?

OST files are integral to the seamless offline operation of MS Outlook. And it's also important when users are online. So backing up offline OST file from Outlook is definitely necessary. Here are some situations where proves that taking a backup of Outlook OST files is valuable:

  • Access Outlook data when Exchange Server is down: In the event of Exchange Server downtime, which can be caused by various factors including viruses or technical issues, an OST file backup ensures you can still open and access your Outlook data without interruption.
  • Restore accidentally deleted Outlook data: There are times when you may mistakenly delete your important Outlook data. However, with a backup of your OST file, data restoration becomes a simple process.
  • Migrate Outlook data to another server: Having OST file backups at your disposal facilitates the seamless transfer of data from one location to another. This is especially useful when migrating to a different email system or server.

How to Backup OST File in Outlook in 3 Easy Ways

In this section, we'll explore three effective ways about how to backup Outlook OST files. You can choose the way you like to secure your offline OST files.

Method 1. Backup Outlook PST Files by Export

You can easily backup OST File to PST format with the Export function of Outlook desktop app. Therefore, you need to ensure that have downloaded Outlook and signed in. Then, you can follow these steps to backup Outlook OST file to PST:

Step 1. Open Outlook, access the File tab, choose Open & Export, then select Import/Export.

Import Export

Step 2. When the Import & Export Wizard appears, select Export to a file, and tap on Next.

Export to a file

Step 3. Choose Outlook Data File (.PST), and then tap Next.

Outlook Data File

Step 4. Select the specific mailbox for export, and don’t forget to tick the Include subfolders box to include all of your mailbox's folders. Then, click Next.

Step 5. Click Browse to select a save location and hit Finish.

Browse USB Flash Drive Location

Method 2. Backup PST File from Outlook with Archive Option

You can also use the Archive option of MS Outlook app to backup OST file in Outlook.

Step 1. Run your Outlook, navigate to the File menu, and choose Options.

Step 2. Click on Mailbox Cleanup, and select Archive.

Outlook Mailbox Cleanup Archive

Step 3. In the Archive dialog box, select Archive this folder and all subfolders. Select the desired files and folders you wish to archive.

Select Folder

Step 4. Browse your computer to choose the destination folder where you want to store the archived data and backup OST file in Windows 10 easily.

Method 3. Backup Outlook PST File Automatically via Third-party Software

In addition to the above methods, you can also use powerful and reliable third-party software to automatically backup OST files in Outlook. AOMEI Backupper Professional is an all-around Outlook backup and restore software. It has several advantages:

🍄 Its Outlook Backup function provides you easy solution to backup Outlook data, including OST files, contacts, etc.
🍄 In addition to Outlook emails, you can use it to backup Yahoo Mail, Gmail, Microsoft 365, and other Outlook desktop-supported emails.
🍄 You can enjoy the flexibility of scheduling backups on a daily, weekly, monthly, or event-triggered basis. And you can enable Wake up computer to run scheduled tasks to set off-peak hours or any time you are not using Outlook to backup OST files automatically.
🍄 It allows you to save a lot of backup time and space by backing up only the changed files with Incremental Backup or Differential Backup.

Please download this powerful backup software on your computer and learn how to take backup of Outlook OST files automatically hassle-free!

Download Free Trial Win 11/10/8.1/8/7/XP
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Step 1. Open the Outlook desktop app, type in your email address and click Connect, then follow the on-screen instructions to add the account containing your OST files.

Add account Outlook

Step 2. Launch AOMEI Backupper Professional software. Click Backup and then Outlook Backup.

Outlook Backup

Step 3. Tap on Add Outlook data to select the Outlook account that contains OST files you want to backup. Then click OK.

Add Outlook Data

Step 4. Click the second box to specify a local path, network or NAS location, or cloud drive to store your Outlook OST files.

Select Backup Destination Path

Step 5. Enable Daily, Weekly, Monthly, Event triggers, or USB plug in auto backup and click Start Backup to backup OST files in Outlook 2019/2016/2013/2010 automatically.

Schedule Settings General

You can change backup method from Incremental Backup (default) to Differential Backup or Full Backup in Backup Scheme.
Except for backup methods, here you can also enable automatic backup cleanup methods, which is helpful for resolving backup disk full.

FAQs about Backing up OST File in Outlook

#1. What is the Difference between OST and PST Files?

PST (Personal Storage Table) and OST (Offline Storage Table) files serve distinct purposes in the context of Outlook email and data management:

PST files are primarily utilized for archiving and backup purposes. They can be stored locally on a user's computer or remotely. PST files provide a convenient way to save and organize older email messages, calendar items, contacts, and other data. Unlike OST files, PST files do not support synchronization with an email server, which means they don't reflect real-time changes made on the server.

OST files are employed for offline access to data stored on an Exchange server. These files are stored on the user's computer and enable users to work with their email, calendar, and other data even when not connected to the server. Changes made in an OST file while offline are synchronized with the Exchange server the next time the computer is connected to the internet. This synchronization ensures that the data is up-to-date and consistent between the client and the server.

#2. What happens if I delete my Outlook OST file?

You can delete OST files. There will be no data loss when you remove OST files as they can be downloaded from Exchange Server again.

#3. What is stored in Outlook OST file?

In general, you typically find the following types of data OST file:

  • Email messages: All your email messages, including those in your inbox, sent items, drafts, and other folders.
  • Calendar items: Appointments, meetings, and events from your Outlook calendar.
  • Contacts: Your contact list, including names, email addresses, phone numbers, and other contact details.
  • Tasks and to-do lists: Any tasks or to-do items you've created in Outlook are part of the data.
  • Notes and Journal entries: Notes you've created and Journal entries for activity tracks.


In summary, it is essential to backup OST file in Outlook to keep your email data accessible offline. While the built-in tools in Outlook are useful, they need you to copy OST files manually when they are changed. Therefore, we suggest using the "Outlook Backup" function of AOMEI Backupper to create an auto backup for your Outlook OST files. This will give you peace of mind and ensure that you can keep your data up-to-date and recover your data quickly should any unexpected event occur.

Besides, you can use this tool to create system backup, disk backup, partition backup, as well as file backup to a lot of locations easily.

Jonna · Editor
Jonna joined AOMEI in 2021 and has become a professional in the areas of computer backup and restoration, disk cloning, file synchronization, etc. She maintains a keen eye for the latest technology trends, ensuring that the information provided is always in step with industry developments.