Fix issue with checkbox in broadcast

broadcast-message.php

@@ -62,7 +62,7 @@ if ($_SERVER['REQUEST_METHOD'] == "POST")
       $recipients = [];
 
       $q = "SELECT username from $table_mailbox WHERE ".db_in_clause("domain", $wanted_domains);
-      if(!isset($_POST['mailboxes_only']) || $_POST['mailboxes_only'] != "on") {
+      if (intval(safepost('mailboxes_only')) == 0) {
          $q .= " UNION SELECT goto FROM $table_alias WHERE ".db_in_clause("domain", $wanted_domains)."AND goto NOT IN ($q)";
       }
       $result = db_query($q);

templates/broadcast-message.tpl

@@ -23,7 +23,7 @@
 	</tr>
 	<tr>
 		<td class="label"><label>{$PALANG.broadcast_mailboxes_only}</label></td>
-		<td><input type="checkbox" name="mailboxes_only"/></td>
+		<td><input type="checkbox" value="1" name="mailboxes_only"/></td>
 	</tr>
 	<tr>
 		<td class="label"><label>{$PALANG.broadcast_to_domains}</label></td>