The code answering to your questions is mostly here https://github.com/dyne/JaroMail/tree/master/src/zlibs and here https://github.com/dyne/JaroMail/tree/master/src

The short answer is: makes it quick (make && make install) to setup all the mutt/fetchmail/abook/notmuch integrated yadayada plus adds whitelisting and folder filtering, both local and remote via sieve.