+@node Server Variables
+@subsection Server Variables
+
+One sticky point when defining variables (both on backends and in Emacs
+in general) is that some variables are typically initialized from other
+variables when the definition of the variables is being loaded. If you
+change the "base" variable after the variables have been loaded, you
+won't change the "derived" variables.
+
+This typically affects directory and file variables. For instance,
+@code{nnml-directory} is @file{~/Mail/} by default, and all @code{nnml}
+directory variables are initialized from that variable, so
+@code{nnml-active-file} will be @file{~/Mail/active}. If you define a
+new virtual @code{nnml} server, it will @emph{not} suffice to set just
+@code{nnml-directory}---you have to explicitly set all the file
+variables to be what you want them to be. For a complete list of
+variables for each backend, see each backend's section later in this
+manual, but here's an example @code{nnml} definition:
+
+@lisp
+(nnml "public"
+ (nnml-directory "~/my-mail/")
+ (nnml-active-file "~/my-mail/active")
+ (nnml-newsgroups-file "~/my-mail/newsgroups"))
+@end lisp
+
+