New post-send hook. Though compose_sent could be a good hook name, it's too similar IMO to compose_send.

src/compose.php

@@ -464,6 +464,7 @@ if ($send) {
         $composeMessage=$compose_messages[$session];
 
         $Result = deliverMessage($composeMessage);
+        do_hook('compose_send_after', $Result, $composeMessage);
         if (! $Result) {
             showInputForm($session);
             exit();