--- a/wp-includes/class-phpmailer.php.orig	2009-05-15 21:32:35.000000000 +0400
+++ b/wp-includes/class-phpmailer.php	2010-11-05 19:30:36.000000000 +0300
@@ -518,8 +518,7 @@
       return false;
     }
 
-    $smtp_from = ($this->Sender == '') ? $this->From : $this->Sender;
-    if(!$this->smtp->Mail($smtp_from)) {
+    if(!$this->smtp->Mail($this->Sender)) {
       $error = $this->Lang('from_failed') . $smtp_from;
       $this->SetError($error);
       $this->smtp->Reset();
@@ -865,9 +864,7 @@
 
     $result .= $this->HeaderLine('Date', $this->RFCDate());
     if($this->Sender == '') {
-      $result .= $this->HeaderLine('Return-Path', trim($this->From));
-    } else {
-      $result .= $this->HeaderLine('Return-Path', trim($this->Sender));
+      $this->Sender = trim($this->From);
     }
 
     /* To be created automatically by mail() */