FAQ 3 - Getting Messages

FAQ 3-1: I just installed Gnus, started it via ‘M-x gnus’ but it only says "nntp (news) open error", what to do?
FAQ 3-2: I'm working under Windows and have no idea what ~/.gnus.el means.
FAQ 3-3: My news server requires authentication, how to store user name and password on disk?
FAQ 3-4: Gnus seems to start up OK, but I can't find out how to subscribe to a group.
FAQ 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?
FAQ 3-6: I want Gnus to fetch news from several servers, is this possible?
FAQ 3-7: And how about local spool files?
FAQ 3-8: OK, reading news works now, but I want to be able to read my mail with Gnus, too. How to do it?
FAQ 3-9: And what about IMAP?
FAQ 3-10: At the office we use one of those MS Exchange servers, can I use Gnus to read my mail from it?
FAQ 3-11: Can I tell Gnus not to delete the mails on the server it retrieves via POP3?