Stellar Mail Converter can convert a variety of email clients, such as Apple Mail, Thunderbird, Postbox, and Outlook for Mac to the other two trending and popularly used email clients: Apple Mail or Outlook for Mac 2011.
The software is very user-friendly in its approach and does the conversion within moments. The only thing that you need to do after the conversion is to import the converted mail database to the respective email client.
Updated on May 27 2019
Note: Although Finder indicates no version number for this application, the developer refers to it as version 188.8.131.52