Softaken OLM to PST Converter Case Study: How a Creative Agency Moved 20 GB+ Mac OLM Archives to Windows
By Georgia Young 22-09-2026 12
For creative agencies, switching from Mac to Windows can present an unexpected challenge in email migration. While employees may be used to working with Outlook on Mac, they can still store their historical mailbox data in OLM files. Those OLM archives can’t just be opened as PST files when the agency switches to Windows-based systems.
This case study presents a real-life case of migration when a creative agency was forced to migrate more than 20GB of Mac Outlook OLM archives to Windows. The aim was to make historic email accessible within Outlook for Windows, retaining important mailbox information such as folders, messages, attachments and timestamps.
Email Migration Challenge
The agency had been using Macs for years. The creative, account management and project teams had amassed a huge volume of email correspondence with clients, vendors and freelancers, and internal teams.
Prior to the hardware upgrade, the agency had 7 Mac-based Outlook OLM archives with a combined size of 22.7 GB.
The archives included:
- Communicating with clients
- Project approvals
- Designs feedback
- Vendor correspondence
- Quotations & Contracts
- Emailed back and forth
- Supporting Documents and Attachments
- Custom folders in Outlook
The company was shifting employees to Windows workstations. The IT team wanted to still have access to the old emails in Outlook on Windows.
The Problem
OLM is tied to Outlook for Mac, and PST is the default Outlook data format for Windows. Simply copying the OLM files to the new Windows computers did not give a straightforward way to use them as normal Outlook PST data.
The Difficulties of the Manual Approach
One option the IT team considered was to use Outlook as a middle man for the migration. This approach however became difficult due to the large number of archives and the amount of historical email data.
Moving thousands of messages by hand would have been a lot of work. It also introduced the ability to miss folders or attachments during the migration.
Another concern was to maintain the existing organization. The agency had created project-specific folders over the years and so losing the folder structure would have made the archived emails much more difficult to use.
So, OLM to PST mass conversion was felt to be more practicable.
Selecting Right Method for OLM to PST Conversion
For this migration scenario, the agency used Softaken OLM to PST Converter to convert the Mac Outlook archives into PST files for working in the Windows environment.
It was more than just changing the file extension. The migration to produce usable PST files that contained the actual email data.
The IT administrator made a backup copy of all seven original OLM files. Thus the source archives were preserved unchanged during the conversion process.
Step-by-Step Migration Process
Step 1: Gather and Arrange the OLM Archives
Seven OLM files were copied to a dedicated migration folder. The IT administrator checked the approximate size of each archive and confirmed that all expected files were present.
Together, they were approximately 22.7 GB in size.
Step 2: Import OLM files
The conversion application was installed on the Windows migration workstation. The administrator then selected the required OLM files and uploaded them into the software.
The mailbox data was displayed for review prior to conversion.
Step 3: Check Mailbox Folders
The administrator looked through folders such as: Inbox, Sent Items, Drafts, and custom project folders.
This step was useful because the agency did not want to convert data that did not need to be converted or lose important project folders.
Step 4: Choose PST as Output Format
The destination format chosen is PST. To keep the converted files organized by employee and department, a separate output location was created.
For example:
- Employee-01.pst
- Employee-02.pst
- Creative-Team.pst
- Accounts-Team.pst
Step 5: Begin the Conversion
Once the necessary OLM data was selected, the conversion was started. Processing time varied from archive to archive because the files contained different amounts of emails and attachments.
During the conversion, the administrator did not run any other heavy applications to ensure that there were enough system resources for the migration.
Step 6. Verify the Converted PST Files
Converted PST files were opened in Outlook on Windows with sample PST files. The IT team sifted through different folders and selected random emails.
They looked at:
- Sender and receiver information
- Subject headings
- Message content
- Timestamps and dates
- Attachments
- Organize your folders
This verification step was critical, because the converted PST files would be the working archives for the new Windows systems.
Migration Result
The agency had PST copies of its historical Mac Outlook data that were converted and verified and could be accessible from the Windows environment.
The migration also provided the IT team with a more structured archive. Alternatively, the agency could give employees Windows-compatible PST archives, instead of retaining the original OLM files as the primary source for historical communication.
The migration scenario involved 22.7 GB of OLM data spread across seven archives, which made manual message-by-message transfer impossible. Having a dedicated conversion workflow means less repetitive work and a structured way to deal with archives.
Key Benefits Noticed
This approach resulted in some practical benefits:
Mac to Windows migration: OLM data may be ready for Windows Outlook.
Bulk processing: large sets of emails could be processed without manual export of each message.
Folder-based selection: You can select the required mailbox folders before conversion.
Attachment preservation: The attachments of the converted emails could be checked.
Better organization: You could create multiple PST files for different employees or departments.
Reduced manual work: The IT team was not required to work through thousands of emails one by one.
Verification before deployment: Sample messages may be checked before deployment of the PST files.
FAQs
1. Why do you need Mac Outlook OLM file conversion to Windows?
Outlook for Mac uses the OLM format for mailbox archives, whereas Outlook for Windows uses PST for local mailbox data. Conversion is a process that makes archived data available for use in the Windows environment.
2. How to Convert Multiple OLM Files?
A dedicated OLM to PST conversion workflow can come in handy when an organization has many archives of Mac Outlook to migrate.
3. Will the old OLM files be deleted?
Do not think of a conversion process as a substitution of original files. It’s a good practice to keep copies of the source OLM archives until after the converted PST files are fully validated.
4. What happens to attachments when converting OLM to PST?
If the conversion software supports it, attachments can be preserved. Always have users open sample converted messages and verify important attachments before completing the migration.
5. Is it possible to open the converted PST files in Windows Outlook?
Yes, PST is intended to be used with Microsoft Outlook including Windows-based Outlook environments that support PST data files.
Conclusion
The process of transferring 20+ GB of Mac Outlook archives to Windows can be complex when there are multiple OLM files and many years of project correspondence. This can be even more problematic when you have thousands of emails, attachments and custom folders to deal with.
In this case-study scenario, the creative agency converted the data from its 22.7 GB archive from seven OLM files to PST files and then verified the results in Windows Outlook. This way, we had a structured path to migrate, and we cut down on the redundant effort of manually moving each individual email.
Organizations who are working on a similar Mac to Windows migration can take Softaken OLM to PST Converter as a part of dedicated OLM to PST conversion workflow. As with any large email migration, it is important to keep source backups and test a representative PST before full deployment.
