Ah, I see - the stuff after the ? needs to be handed to src/compose.php as-is, no encoding.

trunk/squirrelmail/plugins/listcommands/functions.php

@@ -84,6 +84,7 @@ function plugin_listcommands_menu_do() {
 
         /* proto = {mailto,href} */
         $aActions = array_keys($actions);
+        // note that we only use the first cmd/action, ignore the rest
         $proto = array_shift($aActions);
         $act   = array_shift($actions);
 
@@ -95,7 +96,17 @@ function plugin_listcommands_menu_do() {
             } else {
                 $url = "plugins/listcommands/mailout.php?action=$cmd&";
             }
-            $url .= 'send_to=' . urlencode($act);
+
+            // if things like subject are given, peel them off and give
+            // them to src/compose.php as is (not encoded)
+            if (strpos($act, '?') > 0) {
+               list($act, $parameters) = explode('?', $act, 2);
+               $parameters = '&' . $parameters;
+            } else {
+               $parameters = '';
+            }
+
+            $url .= 'send_to=' . urlencode($act) . $parameters;
 
             $links[$cmd] = makeComposeLink($url, $fieldsdescr[$cmd]);