Fix create stanza

mailserver/sieve.md

@@ -8,12 +8,12 @@ It automatically creates a directory for that alias and moves the mail there.
 Then it stops processing.
 
 ```
-require ["fileinto","regex","variables"];
+require ["fileinto","mailbox","regex","variables"];
 
 if allof (header :regex "to" "^<name>.(.*)@<domain.tld>$")
 {
         set :lower :upperfirst "target" "${1}";
-        fileinto "${target}";
+        fileinto :create "${target}";
         stop;
 }
 ```