Mutt

• mbox(5) Format for mail message storage.
• mmdf(5) Multi-channel Memorandum Distribution Facility mailbox format
• mutt_dotlock(1) Lock mail spool files.
• mutt(1) The Mutt Mail User Agent
• muttrc(5) Configuration file for the Mutt Mail User Agent
• smime_keys(1) Utility to add S/MIME certificate to the internal database used by mutt