+If no messages are specified, the default is all messages in the folder.
+However, if no messages are specified and the
+.B \-noall
+switch is enabled, then
+.B sortm
+reports that as an error and exits with non-zero status.
+.B \-noall
+is most useful in the user's profile, to avoid inadvertant sorting of
+an entire folder. The
+.B \-all
+switch can then be used on the command line to disable it. Of course,
+a message specification of
+.I all
+can be used in any case.
+.PP