Mail Archiver X has a free demo mode which has the same functionality as the paid version. The application in demo mode can be used for 12 days. The days are counted for each day the application is used and not as calendar days.
Version 4.2.1 is still 32bit. The upcoming version 4.3 will be 64bit!
Compatibility: High Sierra (10.13) to El Capitan (10.11).
Download a FREE trial of Mail Archiver X: