If you’ve ever needed to open another user OST file, you already know it’s not as simple as double-clicking it in Outlook. These files are locked to the original Outlook profile and Exchange account, which makes accessing them tricky if you don’t have that setup. But here’s the thing: there are real-world situations where you absolutely need to get inside an OST file that isn’t yours, whether for IT management, business continuity, or legal reasons.

This guide breaks down why OST files are hard to access, when you might need to open them, what doesn’t work, and the most reliable ways to finally unlock the data.

What is an OST File and Why Accessing Another User’s File is Difficult

Before we get into solutions, let’s quickly clear up what an OST file is.

An OST (Offline Storage Table) file is Outlook’s way of letting you work with your mailbox even when you’re not connected to the Exchange server. It’s basically a cached copy of your emails, calendar, contacts, and tasks stored locally on your machine.

The catch? Each OST file is tied to the user profile and the Exchange mailbox that created it. That’s why you can’t simply copy an OST from one system to another and expect Outlook to open it. If you try, you’ll usually see errors like “You don’t have permission to access this file” or “This OST file cannot be opened.”

So while the data is sitting there in plain sight, Outlook won’t give you direct access unless you’re logged into the original account.

Real-Life Situations Where You Might Need to Open Another User OST File

It might sound unusual to access someone else’s OST file, but these scenarios come up more often than you’d think:

• Employee departure: An HR or IT department might need to pull old emails after someone leaves the company.

• Legal compliance or audit: Legal teams often need to examine mailbox data stored in OST files.

• System crashes: Outlook profile or Exchange account is gone, but the OST file remains intact.

• Device migration: You’re moving to a new laptop and want to recover email data from an old system.

If you’ve been wondering how to access someone else’s OST file in these situations, you’re not alone. It’s a common IT headache, but thankfully one with reliable solutions.

Why Outlook Alone Won’t Work

Many people try the most obvious route first: just opening the OST file in Outlook. Unfortunately, it doesn’t work. Unlike PST files, which are portable and easy to import, OST files are locked.

You can’t simply “attach” or “import” them into another Outlook profile. Even if you try to access an OST file from different Outlook profile setups, you’ll get blocked because the security keys don’t match.

This is by design. Microsoft doesn’t want OST files to be portable, since they’re meant to work only with the original server mailbox. But when that mailbox no longer exists, this design becomes a barrier instead of a feature.

Manual Methods to Access OST Files

Is there a manual workaround? Sort of, but it comes with limitations.

If you still have access to the original Outlook profile that created the OST, you can open Outlook, then export the mailbox into a PST file. That PST file can then be shared or imported into another Outlook account.

But here are the issues with this approach:

• You must have the original profile active.

• You need Outlook installed on the same machine.

• You need to connect to the original Exchange server at least once.

• If the profile is deleted or the account disabled, this option disappears.

So while exporting works in theory, in practice it fails in most cases where you’re trying to open OST files from old or inactive accounts.

Professional Approach: Using OST File Viewer or Converter Tools

Here’s where third-party tools come in. If you need to view another user’s Outlook OST file or even extract the data into a usable format, professional Free OST Viewer and converters are the most practical solution.

These tools bypass Outlook’s restrictions. They let you:

• Add any OST file, even if it’s orphaned or from another machine.

• Preview the full mailbox, including emails, attachments, contacts, calendar, and notes.

• Export data into PST, EML, MSG, or even Office 365 directly.

• Open OST files from another computer without needing the original account.

For example, IT admins handling employee offboarding often rely on these tools to make sure no mailbox data is lost. A 2023 Spiceworks survey noted that nearly 41% of businesses face difficulties retrieving mailbox data from departed employees, and tools like BitRecover OST to PST Converter solve this exact pain point.

Step-by-Step Guide to Open Another User OST File with a Tool

If you’ve never used one of these tools before, here’s a simple walkthrough using an OST to PST Converter:

1. Download and install the software on your system.

2. Launch the tool and click “Add File.”

3. Browse to the OST file you want to open (this could be from another profile, machine, or user).

4. Preview mailbox contents in the tool’s built-in viewer. You’ll usually see a left-side tree with folders like Inbox, Sent Items, Calendar, etc.

5. Choose Export Options: select PST, MSG, EML, or direct migration to Office 365.

6. Save the file in your preferred location.

7. Open the new PST in Outlook to access the data freely.

That’s it. You’ve just made an inaccessible OST file usable again.

Extra Tips for IT Admins and Business Users

If you’re in IT or handling sensitive user mailboxes, a few extra precautions can make your job easier:

• Always create a backup of the original OST before working with it.

• Use the split PST option if the OST is larger than 20GB. Outlook struggles with very large files.

• Secure sensitive files: if you’re opening OST files for HR or legal purposes, make sure they’re stored on encrypted drives.

• Maintain documentation: if you’re handling another user’s OST for compliance, note who accessed it and why.

These practices keep the process both efficient and secure.

Frequently Asked Questions

1. Can I open another user OST file without Outlook?
Yes, with the help of third-party OST viewers or converters, you can open and read OST files without Outlook installed.

2. Is it legal to open someone else’s OST file?
If you’re doing so as part of your role in IT, HR, or legal compliance within your organization, it’s allowed. Personal or unauthorized access, however, may violate privacy policies.

3. What if the OST file is corrupted?
Professional tools can usually repair and recover data from corrupted OST files before converting them.

4. Can I access OST data without Exchange?
Yes, OST files can be opened without Exchange using a dedicated tool. That’s especially helpful when the original mailbox no longer exists.

Conclusion

The bottom line is this: if you need to open another user OST file, Outlook alone won’t help you. Manual methods only work if you have the original profile and server access, which isn’t always the case. For real-world scenarios—like HR retrieving old emails, IT handling offboarding, or legal teams preparing for audits—the reliable way forward is using an OST viewer or OST to PST converter.