Mutt is an open-source email client for Linux, BSD, and other UNIX-like systems. It is lightweight, highly configurable, and supports a wide range of protocols such as IMAP, POP, SMTP, and S/MIME. Mutt also allows users to read and send emails, as well as manage and organize their email accounts. It has a built-in address book, spell checker, and multiple folder support. Mutt also supports PGP/GPG encryption and supports multiple languages. It is highly customizable, allowing users to change colors, fonts, and layouts. Mutt is an excellent choice for those who need an efficient, secure, and powerful email client.
The discontinued Opera Mail is no longer updated and is no longer supported, but the latest version, 1.0.1044, released in February 2016, can still be downloaded from the official website.