If you want to choose the right way to import OLM to Gmail so can use the efficient tool KDETools OLM to Gmail Migration Tool. OLM to Gmail migration allows checking the preview of mailbox data items & attachment before actual conversion is done.The application allows the user to migrate the oversized OLM files to Gmail without any data loss.
Download and Run KDETools OLM to Gmail Tool.
Click "Add File" and locate Mac OLM file.
Load OLM and fully preview of all items.
Click on Gmail button to Enter Gmail login credentials and click "Convert Now"
Done - Conversion process has been complete.