Have you ever faced a situation of importing your emails from a Mac computer to a PC and stumbled upon a stray file with a mysterious extension ending in .olm? Well, you have just encountered the main file extension type that Microsoft utilizes to secure Mac email data. Let's learn all about what is an OLM file and OLM file.

What is OLM File?

An OLM file is basically a backup file created by Microsoft Outlook on a Mac computer. When you save your work in Outlook on a Mac computer, it stores all your emails, contacts, tasks, calendars and notes in a single file that ends with .olm.

Think of it like a safe and locked storage box for your Mac mail. It is really useful if you want to keep a safe copy of your old emails, clear up space in your email account or move your data from one Mac computer to another.

The main problem with OLM files is that they are developed only for Mac computers. Windows PCs and Outlook for Windows do not allow accessing or opening them by default. Knowing “what is OLM file” helps to understand why there is a need for any method or converter for those who want to transfer emails into a Windows PC.

How Do OLM Files Work?

OLM files are created to store Outlook data on Mac computers in a particular structure. After you press the export button, all your emails, contacts, calendars, and tasks will be archived. They will be compressed as one file to avoid creating thousands of documents.

Furthermore, all the folders in the email will remain in their original structure to ensure users’ ability to locate the required information. Emails and their attachments will also be saved in Outlook items. To extract this archive, one would need to use Mac Outlook, which would recognize the compressed data and transform it into emails. Therefore, the OLM files contain all the information of the user’s account at the moment of exporting. They are also safely stored in Mac computers with a specific coding system, which cannot be recognized by other operating systems.

What is an OLM File Used For?

Mac users use this type of file export to make a safe copy of their emails so that they don’t lose their data in the event that their account becomes inaccessible.
It is helpful to clear out a full inbox by moving old messages and large attachments out of the cloud and onto a computer’s hard drive.
Users use it to migrate their entire Microsoft Outlook history, including contacts and calendars, over to a brand-new Mac computer.
It makes compiling a large archive of old work emails and passing it along to a coworker who also uses a Mac computer much easier.
It lets you read old emails or notes even when you are offline or out of internet for any reason.

Where are OLM files stored?

OLM files don’t exist automatically as a single background file, it is created only when you manually export your data from Microsoft Outlook for Mac.

Where these files are stored depends on two situations:

1. Where you saved your exported OLM File.

When you go to File>Export in Mac Outlook to create an OLM file, the software asks you to save it. By default, it usually saves in:

Downloads folder
Documents folder
Desktop

(If you forgot where you had saved it, open Finder, press Command + F, and search for .olm)

2. Where Outlook Stores Your Profile Data (Raw Files)

If you are searching for the background folder where Mac Outlook actively stores your live email data, contacts, and calendar information (before they are exported to an OLM File), it depends on your Outlook version:

Outlook 2016, 2019, 2021 & Microsoft 365 for Mac:
Users/username/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile

Outlook 2011 for Mac:
Users/username/Documents/Microsoft User Data/Office 2011 Identities/Main Identity

(Note: The Library folder is hidden by default, so to see it, open any Finder window, click on the Go tab at the top of the screen, hold the Option key, and click on Library.)

How to Open OLM File?

Opening an OLM file is easy on Mac, but it is not as simple on Windows. The steps for opening an OLM file depend on the computer you are using .

On a Mac Computer: Open Microsoft Outlook and go to the top toolbar, then click on File > Import. Click on Outlook for Mac archive file (.olm) and choose the file you want to recover, click the Import button. All your emails are now available directly from your Outlook folders.

On Windows PC: Since Windows Outlook is unable to read OLM files, you will be unable to double-click the file to launch it. The first step is to convert the .olm file into a .pst file using a reliable OLM converter tool. Once you have your emails in PST format, you can simply open Windows Outlook and click on File > Open & Export > Import/Export.

These methods show you how to open OLM file and recover your emails saved on your Mac computer on any computer!

How to Open OLM File on a Windows PC?

Since Windows Outlook does not support Mac OLM files, a user can not simply double-click a file to open it. Based on requirement to open an OLM file on Windows PC there are two different ways to go:

Method 1: View OLM Files for Free (Without Outlook)

If you only want to view your emails, attachments and contacts on Windows outlook without installing, you can make use of a free viewer utility. With the help of SysTools OLM viewer software, you can easily view any OLM file contents on your screen without having Outlook installed on your PC.

Method 2: Convert & Import OLM File into Windows Outlook

For Mac users who are willing to move from Mac to Windows and want to import all their old emails into the new Outlook mailbox should consider this method. To achieve this, you may need to convert OLM files into PST, MBOX or PDF. There is one special tool available: SysTools OLM Converter to convert OLM to PST which will allow you to import the converted PST file into Windows Outlook easily.

A Quick Recap

In short, the provided information about the nature of OLM files can help you address the Mac outlook backup and email migration needs better. Although the Outlook software for Mac OS lets you open such files natively and access their content, the application for Windows does not. Thus, if you need to view your emails for free or convert them to PST for Windows Outlook, the right method can help preserve your data, attachments, and folder structure.