+Since the arguments are split by spaces, when there is a variable expansion
+which has an empty result, it will cause the situation that the argument will
+simply be omitted when the program is actually executed by Exim. If the
+script/program requires a specific number of arguments and the expanded
+variable could possibly result in this empty expansion, the variable must be
+quoted. This is more difficult if the expanded variable itself could result
+in a string containing quotes, because it would with the quotes around the
+command arguments. A possible guard against this is to wrap the variable in
+the &%sg%& operator to change any quote marks to some other character.
+.wen
+