How to Migrate OLM File to New Outlook on Mac and Windows?

OLM file is a proprietary mailbox archive file format used only by Outlook for Mac to store a locally available copy of different mailbox items, like email messages, attachments, contacts, calendars, etc. This mailbox archive file is created when you export Mailbox data from the Mac Outlook app.

As this file format is exclusively used by the Mac Outlook app, you cannot import it into the New Outlook desktop client on Windows. Moreover, you cannot even import it into the New Mac Outlook app. This is because it currently doesn’t support the OLM file format. It only supports the PST file format when importing mailbox data.

So, to migrate OLM file to New Outlook, on either platform (Windows or Mac), you may need to convert the mailbox archive to a suitable file format, i:e., PST. In this article, we will explore some ways that you can use to migrate your mailbox data from an OLM file to New Outlook without any hiccups. Let’s read further.

Reasons to Migrate OLM File to New Outlook

Here are some reasons why you may need to migrate your OLM files to the new Outlook on Mac or Windows:

• Switched from an older Mac to a new Mac or Windows 11 system
• Access emails or other mailbox data from an old OLM file in New Outlook
• Merge mailbox data from old Outlook for Mac accounts with the current mailbox data in new Outlook
• To take a backup of old business or personal email communication, contacts, and calendars to a Microsoft 365 or Exchange account(s)

Can You Import an OLM File Directly into New Outlook?

No, you cannot directly import an OLM file into New Outlook for Mac. With the April 2026 update, Microsoft added support for PST files in the New Mac Outlook client. Similarly, the March 2026 update added support for importing PST files into the New Outlook desktop client (Windows). Hence, irrespective of the platform you are on, the email client only supports PST files for importing mailbox data.

Methods to Migrate OLM File to New Outlook

There are two approaches that you can follow to migrate OLM file to New Outlook. One way is to convert the OLM file to PST and then import the resultant file into the new Outlook on either of the platforms. Then, there is also a manual workaround where you need to switch to the legacy Outlook and do so. Let’s look at them.

Method 1: Move Emails from OLM file to New Outlook Account

If you have Outlook installed on your Mac and is configured with Microsoft 365 Business or Enterprise, you may be able to switch back to the classic version and import the OLM file into it. Then, you can revert to the New Outlook to access all your OLM file emails. This workaround is suitable for smaller or a one-off mailbox migration instances. Moreover, it relies on access to classic Outlook for Mac.

However, But if the IT admin or your organization has disabled the toggle to revert to the Legacy Outlook for Mac, or you are on Personal or Family plans of M365, you will not be able to move your emails in this way.

In that case, you will need to convert OLM to PST format to migrate the Outlook for Mac data file to the New Outlook. A quick way to do this is to use an online OLM to PST converter. One such web-based service is Stellar’s online OLM to PST converter. It is a powerful web-based service that lets you conveniently convert a single OLM file of up to 100 MB on a Mac or a Windows PC. All you have to do is upload your OLM file and wait for the service to quickly convert it to PST format.

Some highlights of Stellar OLM to PST Converter online:

• Effortless OLM to PST file conversion process in 3 simple steps: Upload > Convert  > Download
• No dependency on the Outlook client on Mac or Windows
• Supports OLM file exported from Outlook for Mac 2024, 2021, 2019, and earlier
• Works on devices running macOS, Windows, and Linux
• Ensures data privacy by deleting the uploaded and converted files from its servers after 24 hours
• Upgrade to its Premium edition to convert up to 5 OLM files of size ≤5GB.

Limitations of the above workarounds:

• This workaround will not work if you have M365 Personal or Family subscription for Outlook.
• If your organization’s IT admin has disabled reverting from New Outlook to Legacy Outlook, the toggle switch to revert to the Legacy Outlook will be missing or appear to be greyed out.
• The manual workarounds involve several steps, which makes them tedious and time-consuming
• There are chances of missing emails while moving them. Verify the transferred items in the destination mailbox carefully.
• You can only migrate emails from the OLM file into the configured New Outlook account
• The Windows workaround moves items through a configured account and may not be practical for large archives or organization-wide migrations.

Method 2: Migrate OLM File to New Outlook on Windows

If you want to move OLM files to New Outlook on Windows, you can download a Windows-based OLM to PST converter tool that lets you convert OLM file of any size to PST without any file size restrictions. For this, you can use Stellar Converter for OLM. This application works independently of Outlook and allows you to convert OLM to PST accurately, without altering the original mailbox folder structure and hierarchy in the resultant PST file.

You can also use it to directly export data from the OLM file to an existing PST file or a Microsoft 365 profile. The tool can easily handle large OLM files (>45GB) and auto-split the resulting PST file at ~45GB. This helps prevent PST file corruption. Additionally, you can also use it to save the mail items in commonly used file formats such as MSG and EML.

Conclusion

A suitable approach to migrate an OLM file to New Outlook depends on factors like the destination platform (Mac/Windows), access to classic Outlook for Mac, OLM file size, and more. Importing an OLM file or synchronizing emails between the imported OLM file and the configured account can work only when the original Outlook account is accessible. These are suitable only for a small or one-time migration job.

For individuals and organizations, particularly when handling OLM files in bulk, a better way to safely migrate OLM to New Outlook is to use an OLM to PST file converter. For this, you can use Stellar Converter for OLM. Available as an online service or a desktop tool, this software provides a precise way of converting OLM data file(s) to PST format without installing MS Outlook on your system.