If you want to convert OLM to MSG file, I recently used MacSonik OLM Converter for Mac; this software is a top-notch utility for converting OLM files to MSG files easily. Also, this tool supports many different email formats such as PDF, EML, EMLX, CSV, MBOX, GIF, JPG, TIFF, HTML, MHTML, etc. You can convert OLM to various email clients such as Gmail, Office 365, Thunderbird, iCloud, and others. The tool is user-friendly and suitable for both technical and non-technical users. Key features include date range filtering, batch conversion, and the option to split large PST files.

To Know More: https://www.macsonik.com/olm/converter/