Some of Mutt's features include:
- color support
- message threading
- MIME support (including RFC2047 support for encoded headers)
- PGP/MIME (RFC2015)
- various features to support mailing lists, including list-reply
- active development community
- POP3 support
- IMAP support
- full control of message headers when composing
- support for multiple mailbox formats (mbox, MMDF, MH, maildir)
- highly customizable, including keybindings and macros
- change configuration automatically based on recipients, current folder, etc.
- searches using regular expressions, including an internal pattern matching language
- Delivery Status Notification (DSN) support
- postpone message composition indefinetly for later recall
- easily include attachments when composing, even from the command line
- ability to specify alternate addresses for recognition of mail forwarded from other accounts, with ability to set the From: headers on replies/etc. accordingly
- multiple message tagging
- reply to or forward multiple messages at once
- .mailrc style configuration files
- easy to install (uses GNU autoconf)
- compiles against either curses/ncurses or S-lang
- translation into at least 20 languages
- small and efficient
- It's free! (no cost and GPL'ed)