I'm helping a client migrate from Outlook for Mac, and I needed a way to convert an OLM (Mac Outlook) file without keeping Outlook installed. I was surprised that many tools still depend on Outlook just to read the mailbox.

After testing a few options, I found MacSonik OLM Converter , which works directly with OLM files on macOS. It uses its own parsing engine, so it can open and scan OLM files without Outlook. That alone saved a lot of setup time.

Another thing I appreciated was the preview feature. Before exporting, I could browse emails, contacts, calendars, tasks, and mailbox folders to make sure everything looked correct. It also preserved the original folder hierarchy, email metadata (sender, receiver, timestamps, CC/BCC, Message-ID), HTML formatting, inline images, signatures, and attachments.

For larger mailboxes, the software handled batch conversion efficiently, and I liked having options to include or exclude attachments depending on storage needs. Duplicate email detection also helped avoid exporting redundant messages.

On macOS, it exports to PST, PDF, MBOX, EML, MSG, CSV, DOCX, and even migrates directly to Gmail, Microsoft 365, and Yahoo Mail.

Has anyone else found a reliable Mac solution for OLM migration that doesn't require Outlook? I'm curious how it compares with other tools for large mailbox conversions.