I'm preparing to move several users from Outlook for Mac to Microsoft 365, and I wanted to convert each OLM mailbox into PST before importing it into Office 365. Since we're working entirely on Macs, I was looking for a solution that didn't require Windows or Outlook just to open the OLM files.

I recently tested MacSonik OLM Converter, and it handled the migration surprisingly well. It opens OLM files directly using its own scanning engine, so Outlook for Mac isn't required. Before exporting, I could preview emails, contacts, calendars, tasks, and mailbox folders, which helped verify everything before starting the conversion.

The PST output preserved the original folder structure, read/unread status, email flags, timestamps, sender and recipient information, HTML formatting, signatures, inline images, and attachments. That made the imported mailbox in Microsoft 365 look almost identical to the original Outlook for Mac profile.

For larger mailboxes, the software supported batch OLM conversion, duplicate email detection, and automatic PST splitting to prevent oversized Outlook data files. It also supports Unicode, so multilingual emails displayed correctly after migration. Since all processing happens locally on the Mac, I also felt more comfortable from a privacy standpoint.

According to the latest release, version 26.6 includes faster conversion, improved handling of OLM files over 50GB, better compatibility with macOS Sequoia and Sonoma, enhanced Microsoft 365 authentication, and improved support for slightly corrupted OLM files.

For those who've completed an Office 365 migration from Mac Outlook, did you convert your OLM files to PST first, or use another migration approach? I'd appreciate hearing what worked best for your environment.
Try - https://www.macsonik.com/olm/converter/