Index: src/wp-mail.php
===================================================================
--- src/wp-mail.php	(revision 47577)
+++ src/wp-mail.php	(working copy)
@@ -213,7 +213,7 @@
 
 	$post_title = xmlrpc_getposttitle( $content );
 
-	if ( '' === $post_title ) {
+	if ( trim( $post_title ) === '' ) {
 		$post_title = $subject;
 	}