Can I Use PST or OST Files with Outlook 365?
Summary: A lot of Outlook 365 users frequently have questions regarding the kind of database file that Outlook 365 uses to keep mail items locally stored. Which is it—PST or OST? The purpose of this post is to address this query and elucidate the distinctions between OST and PST files as well as their different functions within Outlook 365.
Outlook data files known as the Offline Storage Table (OST) and Personal Storage Table (PST) hold a synced local duplicate of mailbox contents such as emails, attachments, contacts, notes, and more. The process of adding a new email account in Microsoft Outlook results in the creation of an Outlook data file. Email accounts and Outlook versions determine whether PST or OST files are created by Outlook for mailbox storage.
For example, when you add an Exchange Server, Microsoft 365 (formerly Office 365), Outlook.com, or IMAP email account, Outlook creates an OST file to store mail items locally. Nevertheless, the email client produces and saves the email and other mail items in a PST data file if you add or log in to Outlook using a POP email account.
So, the question is: which file format does Outlook 365 use—OST or PST? The quick response to your query is that Outlook 365 makes use of both PST and OST files. We’ll discover how Outlook 365 utilizes OST and PST files in this piece.
Overview – Outlook 365
The Microsoft 365 Office package includes Outlook 365. It provides a feature-rich email, calendar, contacts, and task management system. It is a complete professional tool because it also enables users to manage their contacts, emails, and appointments in an orderly fashion.
What Is the Difference between an OST File and a PST File?
Outlook 365 is connected to both OST and PST files, however they have different functions and features. Let’s compare the two files based on a few different criteria.
| Features | OST | PST |
| Email Accounts | Designed for Outlook 365, IMAP, and Exchange accounts | Generated during the Outlook POP email account setup |
| Accessibility | Limited to the initial MAPI profile and encrypted using the GUID for MAPIEntry. | Accessible and importable with any Outlook profile |
| File Size | Size limit of up to 4 PB (Outlook 2007’s default limitations are 20 GB; Outlook 2010 and newer versions have 50 GB.) | Maximum file size of 4 PB (Outlook 2007 default limitations are 20 GB; Outlook 2010 and newer versions have default limits of 50 GB.) |
| Security | Requires authentication from the associated MAPI profile and is encrypted using the MAPIEntryID GUID key. | Not by default encrypted. Easily transferred or copied |
| Advantages | Gives offline access when the network is unstable. | Utilized for relocation and backup |
| Disadvantages | More durable yet susceptible to harm by viruses, malware, or problems with profiles | Corruptible in nature. could become unstable or unreachable if it gets too big. |
| Corruption Fix | For corruption problems, use ScanPST.exe; for data extraction from OST files, use CubexSoft OST to PST Converter. | Use the Inbox Repair Tool, ScanPST.exe, to resolve corruption problems. |
| Password Protect | Not directly possible to secure with a password | Can be password-protected using the Outlook Import/Export Wizard before exporting. |
| Supported by | Office 365, IMAP, and Exchange | Exchange, Office 365 |
Outlook 365’s Use of PST Files
PST files are used to locally store mailbox data from web-based and POP3 mail accounts on the user’s PC. PST files, however, have different functions in Outlook 365, such as:
- Keeping old emails in the archive
- Generating backups for mailboxes
- Transferring mailbox contents between various email addresses
Outlook 365’s PST File Benefits
PST files are locally stored files that include mailbox contents like emails, attachments, contacts, messages, and so on. But no local updates are stored in the PST file. Rather, it retrieves the emails from the mailbox server, and any modifications are instantly updated on the server.
Here are some of the PST file’s main benefits:
- Assists in controlling mailbox size
- Optimize Outlook 365 performance by moving mail items from big OST files to PST files.
- Make copies of everything.
- Exchange, Microsoft 365, Outlook for Mac, and other mailbox servers can all open PST files.
- Transfer data between mailbox servers or accounts (MS Exchange, Microsoft 365, etc.)
- Interoperability across many devices
- Password protection is an option to prevent unwanted access.
PST File Restrictions
PST files also have several drawbacks and restrictions, including:
- They are prone to corruption.
- Outlook performance problems, such as delays in sending and receiving new emails, can be caused by large PST files.
- It is well known that oversized PST files can have integrity problems that cause harm, corruption, and data loss.
OST Files’ Usage in Outlook 365
Outlook users can access their mailbox contents via an OST file, commonly referred to as an offline folder, even if their computer is offline or not connected to the mail server or the internet. Even with a shaky or inconsistent connection, Outlook continues to function flawlessly.
When a user sets up an Exchange, Microsoft 365, Outlook.com, or IMAP email account, an OST file is generated. Outlook stores a synchronized copy of the user’s mailbox data in an OST file that is automatically created at the %localappdata%/Microsoft/Outlook directory.
All of the modifications are kept in the local OST file rather than on the server itself. When a user is not connected to the Exchange, Microsoft 365, Outlook.com, or IMAP server, they can still work with their emails, contacts, and calendar items thanks to this capability, which is also known as Cached Exchange Mode. Outlook modifications that are kept in the local cache, or the OST file, synchronize with the mailbox server once the connection is restored.
The Advantages of Outlook 365’s OST files
When it comes to Outlook 365, OST files have various advantages. Among these are:
- Enables offline access to mailbox contents, which are encrypted by default to prevent unwanted access to the mail items
- Reduces the amount of reading and writing
- Enhances Outlook and server functionality
- less prone to wrongdoing
- Allows users to read, write, and delete messages without continuously using up network bandwidth.
- Despite the lack of internet, enables users to access their emails and carry out their tasks.
- Helpful for people who frequently travel or struggle to get a stable network connection
Restriction of OST Files
The OST file cannot be imported into other Outlook profiles or accounts since it is encrypted by default using the MAPIEntryID GUID key. By default, the machine and user account from which the OST file originated are linked. This increases the difficulty for users to retrieve their material from another device if Outlook malfunctions or the user encounters issues with the OST data file.
In situations like these, you can download and set up a sophisticated OST File to PST Converter program, like CubexSoft OST Converter. With the use of the software, mail items from OST files that are too large, unreadable, orphaned, or encrypted can be recovered and saved in PST format, which you can then import into any Outlook account.
Conclusion
Outlook 365 stores mailbox data in both PST and OST formats. By default, when you add an Exchange, Microsoft 365, Outlook.com, or IMAP account to Outlook 365, an OST file is created. On the other hand, Outlook saves mail items in a PST file if you back up an OST file or archive mail items.
Likewise, users can export mail items from an OST file to a PST file using the Outlook Import Export procedure for backup purposes. After that, they can import this file to move the mailbox data or restore mail items into any other Outlook account, Exchange Server, or Microsoft 365.
