OST to PST Info

What is an OST File?

An OST (Offline Storage Table) file is a Microsoft Outlook data file that stores a synchronized copy of your mailbox information when you're using Microsoft Exchange Server or Microsoft 365 accounts. These files allow you to work with your emails, calendar, contacts, and other Outlook items even when you're disconnected from the server.

How OST Files Work

When you configure an Exchange account in Outlook, a local OST file is created on your computer. This file maintains a synchronized copy of your mailbox data from the Exchange server. When you're connected to the server, changes you make in Outlook are synchronized with the server, and vice versa. When you're offline, you can still access and work with your Outlook data, and any changes you make will be synchronized with the server once you reconnect.

OST File Location

By default, OST files are stored in the following locations depending on your Windows version:

• Windows 10/8/7: C:\Users\[username]\AppData\Local\Microsoft\Outlook
• Windows XP: C:\Documents and Settings\[username]\Local Settings\Application Data\Microsoft\Outlook

The filename typically follows the pattern: [email_address].ost

OST File Size Limitations

The maximum size of an OST file depends on the version of Outlook you're using:

• Outlook 2007: 20 GB
• Outlook 2010: 50 GB
• Outlook 2013, 2016, 2019, and Microsoft 365: 50 GB

However, performance may degrade as the file size increases, so it's recommended to keep your OST file size manageable.

Common OST File Issues

OST files can sometimes encounter problems, including:

• Corruption: OST files can become corrupted due to improper Outlook shutdowns, system crashes, or hardware failures.
• Synchronization Issues: Sometimes, changes made offline may not properly sync with the Exchange server.
• Size Limitations: When an OST file approaches its size limit, Outlook performance may degrade.
• Orphaned OST Files: If an Exchange account is removed from Outlook but the OST file remains, it becomes orphaned and inaccessible.

Fixing OST File Issues

Here are some common methods to resolve OST file issues:

1. Use Outlook's Inbox Repair Tool (SCANPST.EXE): This tool can help repair minor corruption issues in OST files.
2. Recreate the OST File: You can delete the existing OST file and let Outlook create a new one by resyncing with the Exchange server.
3. Convert OST to PST: If you need to access an orphaned OST file, converting it to PST format can help recover the data.
4. Archive Old Emails: To manage OST file size, regularly archive older emails to separate PST files.

Differences Between OST and PST Files

While both OST and PST files store Outlook data, they have several key differences: