NeoMutt can be installed with Homebrew.
The instructions for installing Homebrew are provided on the Homebrew homepage.
Once you have Homebrew installed, then getting NeoMutt is as simple as:
$ brew install neomutt
Homebrew automatically updates itself when you run a
brew command. It never
updates a package, such as NeoMutt, unless you tell it to.
When Homebrew itself is updated, it checks to see if the NeoMutt package definition has been updated, as would be the case shortly after a new version of NeoMutt is released. You will only be able to install the latest release of NeoMutt if Homebrew is up-to-date. You can check this by updating Homebrew manually.
$ brew update
To upgrade NeoMutt to the latest version, run:
$ brew upgrade neomutt
To remove NeoMutt from your system, run:
$ brew uninstall neomutt
This command will not remove any files from your home directory, such as NeoMutt configuration files.