Each source file in the library provides a group of related functions.

File	Description
mutt/array.h	Linear array API
mutt/base64.c	Conversion to/from base64 encoding
mutt/buffer.c	General purpose object for storing and parsing strings
mutt/charset.c	Conversion between different character encodings
mutt/date.c	Time and date handling routines
mutt/envlist.c	Private copy of the environment variables
mutt/exit.c	Leave the program NOW
mutt/file.c	File management functions
mutt/filter.c	Pass files through external commands (filters)
mutt/hash.c	Hash Table data structure
mutt/list.c	Singly-linked list type
mutt/logging.c	Logging Dispatcher
mutt/mapping.c	Map between a string and a constant
mutt/mbyte.c	Multi-byte String manipulation functions
mutt/md5.c	Calculate the MD5 checksum of a buffer
mutt/memory.c	Memory management wrappers
mutt/notify.c	Notification API
mutt/observer.h	Observer of notifications
mutt/path.c	Path manipulation functions
mutt/pool.c	A global pool of Buffers
mutt/prex.c	Manage precompiled / predefined regular expressions
mutt/random.c	Random number/string functions
mutt/regex.c	Manage regular expressions
mutt/slist.c	A separated list of strings
mutt/signal.c	Signal handling
mutt/state.c	Keep track when processing files
mutt/string.c	String manipulation functions

Note: The library is self-contained – some files may depend on others in the library, but none depends on source from outside.