Here are some examples:
@table @code
-@item [unread]
-Display only unread articles.
+@item [read]
+Display only read articles.
@item [not expire]
Display everything except expirable articles.
groups.
@item charset
-@item charset
+@cindex charset
Elements that look like @code{(charset . iso-8859-1)} will make
@code{iso-8859-1} the default charset; that is, the charset that will be
used for all articles that do not specify a charset.
See also @code{gnus-group-charset-alist}.
@item ignored-charsets
-@item ignored-charset
+@cindex ignored-charset
Elements that look like @code{(ignored-charsets x-known iso-8859-1)}
will make @code{iso-8859-1} and @code{x-unknown} ignored; that is, the
default charset will be used for decoding articles.
@sc{nov} databases for the incoming mails. This makes it the fastest
backend when it comes to reading mail.
+@cindex self contained nnml servers
+When the marks file is used (which it is by default), @code{nnml}
+servers have the property that you may backup them using @code{tar} or
+similar, and later be able to restore them into Gnus (by adding the
+proper @code{nnml} server) and have all your marks be preserved. Marks
+for a group is usually stored in the @code{.marks} file (but see
+@code{nnml-marks-file-name}) within each @code{nnml} group's directory.
+Individual @code{nnml} groups are also possible to backup, use @kbd{G m}
+to restore the group (after restoring the backup into the nnml
+directory).
+
Virtual server settings:
@table @code
@vindex nnml-directory
All @code{nnml} directories will be placed under this directory.
The default is the value of `message-directory' (whose default value is
-@file{~/Mail})
+@file{~/Mail}).
@item nnml-active-file
@vindex nnml-active-file
@item nnml-get-new-mail
@vindex nnml-get-new-mail
If non-@code{nil}, @code{nnml} will read incoming mail. The default is
-@code{t}
+@code{t}.
@item nnml-nov-is-evil
@vindex nnml-nov-is-evil
If non-@code{nil}, this backend will ignore any @sc{nov} files. The
-default is @code{nil}
+default is @code{nil}.
@item nnml-nov-file-name
@vindex nnml-nov-file-name
@vindex nnml-prepare-save-mail-hook
Hook run narrowed to an article before saving.
+@item nnml-marks-is-evil
+@vindex nnml-marks-is-evil
+If non-@code{nil}, this backend will ignore any @sc{marks} files. The
+default is @code{nil}.
+
+@item nnml-marks-file-name
+@vindex nnml-marks-file-name
+The name of the @sc{marks} files. The default is @file{.marks}.
+
@end table
@findex nnml-generate-nov-databases
@cindex mh-e mail spool
@code{nnmh} is just like @code{nnml}, except that is doesn't generate
-@sc{nov} databases and it doesn't keep an active file. This makes
-@code{nnmh} a @emph{much} slower backend than @code{nnml}, but it also
-makes it easier to write procmail scripts for.
+@sc{nov} databases and it doesn't keep an active file or marks file.
+This makes @code{nnmh} a @emph{much} slower backend than @code{nnml},
+but it also makes it easier to write procmail scripts for.
Virtual server settings:
will add extra headers to keep track of article numbers and arrival
dates.
+@cindex self contained nnfolder servers
+When the marks file is used (which it is by default), @code{nnfolder}
+servers have the property that you may backup them using @code{tar} or
+similar, and later be able to restore them into Gnus (by adding the
+proper @code{nnfolder} server) and have all your marks be preserved.
+Marks for a group is usually stored in a file named as the mbox file
+with @code{.mrk} concatenated to it (but see
+@code{nnfolder-marks-file-suffix}) within the @code{nnfolder} directory.
+Individual @code{nnfolder} groups are also possible to backup, use
+@kbd{G m} to restore the group (after restoring the backup into the
+@code{nnfolder} directory).
+
Virtual server settings:
@table @code
If non-@code{nil}, this backend will ignore any @sc{nov} files. The
default is @code{nil}.
+@item nnfolder-nov-file-suffix
+@vindex nnfolder-nov-file-suffix
+The extension for @sc{nov} files. The default is @file{.nov}.
+
+@item nnfolder-marks-is-evil
+@vindex nnfolder-marks-is-evil
+If non-@code{nil}, this backend will ignore any @sc{marks} files. The
+default is @code{nil}.
+
+@item nnfolder-marks-file-suffix
+@vindex nnfolder-marks-file-suffix
+The extension for @sc{marks} files. The default is @file{.mrk}.
+
@end table