Sup is a console-based email client written in Ruby, designed for heavy email users who prefer a keyboard-driven, terminal interface. It provides a Gmail-like workflow with thread-centric conversation view, labeling (tags), archiving, muting, and full-text search powered by Xapian. The application supports multiple local mail sources (mbox and Maildir), multiple accounts, and can be extended via Ruby hooks. It runs as a full-screen ncurses application with a buffer-based window manager, offering modes for inbox, search results, compose, reply, forward, and more. Architecturally, Sup follows a modular pattern with manager classes (PollManager, UpdateManager, UndoManager, DraftManager, etc.) that encapsulate state and behavior. The UI is built on a Mode hierarchy with a shared keymap DSL, allowing consistent keyboard navigation across different views. The core data flow involves polling mail sources, parsing messages with RMail, threading them using a JWZ-inspired algorithm, and indexing them into a Xapian database for fast search. Labels and state are persisted in YAML files and the Xapian index. Key entry points include the main `bin/sup` TUI, `bin/sup-sync` for index synchronization, `bin/sup-add` for adding sources, and various utility scripts. External dependencies include ncursesw, RMail, Xapian, GPGME, and Chronic for date parsing. The project is in maintenance mode, focusing on stability and bug fixes rather than new features, but remains actively maintained with CI across many Ruby versions.