How to Extract Email Addresses from Outlook PST and OST Files

What PST and OST Files Are

If you have used Microsoft Outlook for any length of time, you probably have PST or OST files sitting on your computer. These are the archive files that Outlook uses to store your emails, contacts, calendar entries, and other data.

PST (Personal Storage Table) is the older format. It stores a local copy of your mailbox data that you can move, back up, and open on different machines. When you export from Outlook or create a local backup, you typically get a PST file.

OST (Offline Storage Table) is used by Outlook when connected to Exchange or Microsoft 365. It keeps a synchronised copy of your mailbox on your local machine so you can work offline. OST files are tied to the specific Outlook profile and cannot be moved directly to another machine.

Both file types contain email addresses throughout. Every email you sent or received, every contact entry, every calendar invitation. There are addresses everywhere inside these files.

The Challenge with PST and OST Files

Here is the thing. Email Extractor supports MSG and EML files directly, but PST and OST files are complex database-like containers that hold hundreds or thousands of individual messages. They are not simple text files that you can just upload and scan.

So you need an intermediate step. You need to either export individual messages from the PST file, or export your contacts as a separate file, before running extraction. This sounds like extra work, but it is actually quite straightforward, and I will walk through the options.

Method 1: Export Contacts from Outlook as CSV

If what you mainly want is the contact addresses stored in your Outlook contacts, this is the simplest approach.

1. Open Microsoft Outlook
2. Go to File → Open & Export → Import/Export
3. Select "Export to a file"
4. Choose "Comma Separated Values" as the file type
5. Select the Contacts folder
6. Choose where to save the CSV file
7. Click Finish

Now you have a CSV file containing all your Outlook contacts with their email addresses. Upload this to Email Extractor and extract the addresses.

This method gets you the addresses from your contact list specifically. If you want addresses from actual email messages (senders, recipients, addresses mentioned in email bodies), you need one of the other methods.

Method 2: Export Messages as MSG Files

Outlook lets you save individual messages or groups of messages as MSG files, and Email Extractor supports MSG files natively.

For individual messages:

1. Open the email in Outlook
2. Go to File → Save As
3. Choose "Outlook Message Format (*.msg)"
4. Save the file

For multiple messages:

1. Select the messages you want (Ctrl+Click or Shift+Click)
2. Drag them to a folder on your desktop or in File Explorer
3. Each message saves as a separate MSG file

Then upload the MSG files to Email Extractor. The tool will scan through the headers and body of each message, pulling out every email address it finds.

This method works well when you want addresses from a specific folder or time period. Select the relevant messages, save them out, and extract.

Method 3: Convert PST to MBOX

If you have a large PST file and want to extract from the entire thing, converting it to MBOX format gives you a file that is more accessible. MBOX is a standard email archive format that stores messages as plain text.

There are several free tools that convert PST to MBOX:

• readpst (part of libpst on Linux/Mac): A command-line tool that converts PST files to MBOX format. Run readpst -o output_folder archive.pst and it creates MBOX files for each folder.
• Thunderbird with ImportExportTools NG: Import the PST file into Thunderbird, then export as MBOX using the addon.
• Various free PST viewer tools: Some allow you to open a PST and export messages in different formats.

Once you have the MBOX file, you can extract from it. We have a detailed guide on extracting from MBOX files including Gmail Takeout that covers the process.

Method 4: Use Outlook's Search and Export

If you only need addresses related to a specific topic or contact, Outlook's search can narrow things down before you export.

1. In Outlook, use the search bar to find relevant messages
2. Search by sender, date range, keyword, or folder
3. Select the search results you want
4. Save them as MSG files (drag to a folder)
5. Upload the MSG files to Email Extractor

This targeted approach gives you cleaner results than extracting from an entire archive. You get addresses that are actually relevant to what you are looking for rather than every address from years of email history.

Dealing with Large PST Archives

PST files can be enormous. Long-running Outlook archives can exceed 10 GB. Trying to process the entire thing at once is not practical.

Better strategies:

Export by folder. Instead of the whole PST, export specific folders. Maybe you only need addresses from your Sent Items, or from a specific project folder. Export just those folders as MSG files or CSV.

Export by date range. Most PST tools and Outlook's own export wizard let you filter by date. If you only need contacts from the last two years, limit your export accordingly.

Split the work. Process one folder or time period at a time. Extract, download the results, then move on to the next batch. Merge the lists afterwards and remove duplicates.

OST Files Specifically

OST files are trickier than PST files because they are tied to an Outlook profile and cannot be opened directly. You have a few options:

If Outlook is working normally: Just export from Outlook directly using the methods above. The OST file is being read by Outlook in the background, and you do not need to interact with it directly.

If Outlook is not available or the profile is damaged: Some third-party tools can open OST files independently and convert them to PST or other formats. This is more of a data recovery scenario.

If you are migrating away from Outlook: Export everything to PST first (File → Open & Export → Import/Export → Export to a file → Outlook Data File), then use the PST methods described above.

What You Will Find in Outlook Archives

Outlook archives contain several types of email addresses:

Email Extractor finds all of these when you export the data to a supported format. The results can be quite extensive if you have years of email history, which is why cleaning up the list afterwards is important.

Combining Outlook Data with Other Sources

If you use Outlook alongside other email or communication tools, you might want to combine extracted addresses from multiple sources. For example, addresses from your Outlook archive plus addresses from a Gmail Takeout export, or contacts from a Slack export.

Email Extractor handles multiple file types in a single session. So you could upload MSG files from Outlook, an MBOX file from Gmail, and a JSON export from Slack all together, and get one combined, deduplicated list.

Privacy Note

Outlook archives contain personal and business communications. Everything Email Extractor processes stays in your browser. No files are uploaded to any server. This is particularly important for business email archives, which may contain confidential or legally privileged communications.

Be mindful about what you do with extracted addresses from email archives. These are addresses of people who communicated with you in specific contexts. Use them appropriately and within whatever policies your organisation has around contact data handling.

For broader guidance on responsible extraction practices, see our privacy guide.

Can I upload a PST file directly to Email Extractor?

No, PST files are complex binary databases that Email Extractor does not read directly. You need to export the content to a supported format first, either as CSV contacts, MSG files for individual messages, or MBOX for bulk conversion. The methods described in this guide cover all the practical approaches.

What if I have a very old PST file from an earlier version of Outlook?

Older PST files (ANSI format, from Outlook 2002 and earlier) are smaller and use a different internal structure, but the same export methods work. If you can open the PST in a current version of Outlook, you can export from it. If you cannot open it, a tool like readpst can usually handle older formats.

Will I get duplicate addresses from my Outlook archive?

Almost certainly yes, especially from your Inbox and Sent Items where the same people appear in many messages. Email Extractor removes duplicates automatically, so the list you download will have each unique address only once.