If you have MacPorts installed, then getting NeoMutt is as simple as:
port install neomutt
These instructions will help you install all the dependencies you’ll need to build NeoMutt from the source code.
Now you can follow the guide for building NeoMutt.
These instructions will help you install all the dependencies you’ll need to debug NeoMutt.
Now you can follow the guide for debugging NeoMutt.