+Because
+.B mhpath
+expands and sorts
+.RI [ msgs ].
+the command
+.PP
+.RS 5
+.nf
+mv `mhpath 501 500`
+.fi
+.RE
+.PP
+to will not move 501 to 500.
+Quite the reverse. But
+.PP
+.RS 5
+.nf
+mv `mhpath 501` `mhpath 500`
+.fi
+.RE
+.PP
+will do the trick.
+.PP
+Out of range message 0 is treated far more severely than large out of
+range message numbers.