I suggest you use Export Mac OLM to Gmail Converter which allows users to save data in various file formats like EML, EMLX, Zimbra, MSG, HTML, etc. Users can batch convert OLM to Gmail file to select single and multiple files using the batch feature. This software imports emails, calendars and contacts for Gmail accounts from UNICODE / ANSI files.https://www.kdetools.com/mac/olm/gmail/