diff --git a/src/Transport/Sendmail.php b/src/Transport/Sendmail.php
index 412763ab..9be0137f 100644
--- a/src/Transport/Sendmail.php
+++ b/src/Transport/Sendmail.php
@@ -217,15 +217,14 @@ protected function prepareBody(Mail\Message $message)
      */
     protected function prepareHeaders(Mail\Message $message)
     {
-        // On Windows, simply return verbatim
-        if ($this->isWindowsOs()) {
-            return $message->getHeaders()->toString();
-        }
-
-        // On *nix platforms, strip the "to" header
+        // strip the "subject" header
         $headers = clone $message->getHeaders();
-        $headers->removeHeader('To');
         $headers->removeHeader('Subject');
+
+        // On *nix platforms, strip the "to" header as well
+        if (!$this->isWindowsOs()) {
+            $headers->removeHeader('To');
+        }
         return $headers->toString();
     }