diff -r 2873f4971281 Lib/smtplib.py
--- a/Lib/smtplib.py	Wed Mar 20 18:16:05 2013 +0200
+++ b/Lib/smtplib.py	Thu Mar 21 00:18:00 2013 +0530
@@ -751,7 +751,10 @@
                 esmtp_opts.append(option)
         (code, resp) = self.mail(from_addr, esmtp_opts)
         if code != 250:
-            self.rset()
+            if code == 421:
+                self.close()
+            else:
+                self.rset()
             raise SMTPSenderRefused(code, resp, from_addr)
         senderrs = {}
         if isinstance(to_addrs, str):
@@ -760,13 +763,19 @@
             (code, resp) = self.rcpt(each, rcpt_options)
             if (code != 250) and (code != 251):
                 senderrs[each] = (code, resp)
+            if code == 421:
+                self.close()
+                raise SMTPRecipientsRefused(senderrs)
         if len(senderrs) == len(to_addrs):
             # the server refused all our recipients
             self.rset()
             raise SMTPRecipientsRefused(senderrs)
         (code, resp) = self.data(msg)
         if code != 250:
-            self.rset()
+            if code == 421:
+                self.close()
+            else:
+                self.rset()
             raise SMTPDataError(code, resp)
         #if we got here then somebody got our mail
         return senderrs
diff -r 2873f4971281 Lib/test/test_smtplib.py
--- a/Lib/test/test_smtplib.py	Wed Mar 20 18:16:05 2013 +0200
+++ b/Lib/test/test_smtplib.py	Thu Mar 21 00:18:00 2013 +0530
@@ -807,6 +807,9 @@
         with self.assertRaises(smtplib.SMTPResponseException) as error:
             with smtplib.SMTP(HOST, self.port) as smtp:
                 smtp.noop()
+        # Next two asserts make sure that smtp.close() was called
+        self.assertIsNone(smtp.sock)
+        self.assertIsNone(smtp.file)
         self.assertEqual(error.exception.smtp_code, 421)
         self.assertEqual(error.exception.smtp_error, b'QUIT FAILED')
         # We don't need to clean up self.serv.quit_response because a new