FAQ 3 - Getting Messages

[3.1]: I just installed Gnus, started it via `M-x gnus' but it only says "nntp (news) open error", what to do?
[3.2]: I'm working under Windows and have no idea what ~/.gnus.el means.
[3.3]: My news server requires authentication, how to store user name and password on disk?
[3.4]: Gnus seems to start up OK, but I can't find out how to subscribe to a group.
[3.5]: Gnus doesn't show all groups / Gnus says I'm not allowed to post on this server as well as I am, what's that?
[3.6]: I want Gnus to fetch news from several servers, is this possible?
[3.7]: And how about local spool files?
[3.8]: OK, reading news works now, but I want to be able to read my mail with Gnus, too. How to do it?
[3.9]: And what about IMAP?
[3.10]: At the office we use one of those MS Exchange servers, can I use Gnus to read my mail from it?
[3.11]: Can I tell Gnus not to delete the mails on the server it retrieves via POP3?