If you wish to migrate your Outlook for Mac mailbox data to cloud-based Office 365, you require a professional OLM to Office 365 migrator like Kernel for OLM to PST Converter. It provides multiple saving or exporting options. You can save Outlook for Mac OLM files in different formats such as MSG, EML, RTF, HTML, TXT, MHTML, MBOX, IMAP and DBX. You can try its free demo version before purchasing it. www.olmtooffice365migration.com.