Gnus
A newsreader and email client for Emacs
Gnus can be difficult to use, especially if you can't remember the keybindings (you could say that about all of Emacs). This page is here to remind me of the most widely used keybindings and to have a central place for useful links.
Links
Homepage: http://www.gnus.org/
Manuals page: http://www.gnus.org/manual.html
Big Monolithic Manual: http://www.gnus.org/manual/big-gnus.html
A very good introduction: http://www.xemacs.org/Links/tutorials_3.html
Vocabulary and Model
Gnus uses a somewhat specialized vocabulary. It's important that one knows it (somewhat) before trying to configure Gnus. Everything is an uphill battle otherwise.
The main thing to remember is that is Gnus was designed primarily as a newsreader. All the terms Gnus uses tend to revolve around that idea. Yes, you can use Gnus to read your email effectively, but because Gnus is primarily a newsreader, the email concepts tend to get expressed in "newsreader" terms.
So where Gnus uses the term "server", it usually means "news server". News servers have lists of news groups that you can subscribe to. Each group has a list of messages that you can view and can, potentially, be posted to. Gnus uses the term "select method" interchangably with this concept of "server". It's important to understand this message model when it comes time to configure email.
So, servers, have groups, and groups have messages. In email, groups of messages are called "folders" but not in Gnus. Since Gnus treats everything like news, folders of messages are called "groups", just like Usenet. The root of all your email groups is the "server" or "select method". So, if you have a bunch of maildir folders, the root directory of that bunch of maildir folders is what Gnus would call the "server" or "select method", since this is the corresponding email concept - it's the entity which logically contains all the groups (folders) you want to read.
Finally, servers have backends. This tells Gnus how to actually read the email/news.