I like to suggest you to use Mac OLM to Gmail converter tool to successfully migrate OLM to Gmail Import. The tool helps user to export email files, email contact attachments, calendars, attachments, tasks, notes, folders, etc. It extracts all the important components of the email like To, Bcc, CC, Sent, From, Received, Attachments, etc. The application also supports email servers like Office 365 and Exchange Server accounts.