Gnus 5.10 Reference Manual

Gnus is a flexible message reader running under GNU Emacs. It supports reading and composing both news and mail. In addition, it is able to use a number of web-based sources as inputs for its groups.
The main Gnus goal is to provide the user with an efficient and extensible interface towards dealing with large numbers of messages, no matter the form they may have or wherever they may come from.
Gnus is a fully MIME-compliant and supports reading and composing messages using any charset that GNU Emacs supports.