From iA wiki
See also E-Mail Clients | Newsreaders | Emacs
Home Page: http://www.gnus.org
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.
It is very extensible and efficient, it permits to deal with large numbers if messages, it supports messages in
various forms and from various types of source (NNTP, POP3, IMAP, HTTP, mbox files, maildirs, etc...).
Gnus is fully MIME-compliant and supports reading and composing messages using any charset that GNU Emacs supports.
More informations (including documentation, references to related mailing lists and newsgroups and other resources) can be found at the Gnus web site.