diff -r 49533a9fe322 Lib/smtplib.py
--- a/Lib/smtplib.py    Thu Sep 08 20:50:03 2016 -0700
+++ b/Lib/smtplib.py    Fri Sep 09 12:36:18 2016 +0300
@@ -241,7 +241,6 @@
         will be used.
 
         """
-        self._host = host
         self.timeout = timeout
         self.esmtp_features = {}
         self.command_encoding = 'ascii'
@@ -328,6 +327,7 @@
                     port = int(port)
                 except ValueError:
                     raise OSError("nonnumeric port")
+        self._host = host
         if not port:
             port = self.default_port
         if self.debuglevel > 0:
diff -r 49533a9fe322 Lib/test/test_smtplib.py
--- a/Lib/test/test_smtplib.py  Thu Sep 08 20:50:03 2016 -0700
+++ b/Lib/test/test_smtplib.py  Fri Sep 09 12:36:18 2016 +0300
@@ -149,6 +149,15 @@
                               re.MULTILINE)
         self.assertRegex(stderr.getvalue(), expected)
 
+    def test_explicit_connect(self):
+        mock_socket.reply_with(b"220 Hello world")
+        # create instance without arguments
+        smtp = smtplib.SMTP()
+        # .connect must set ._host since it is used by .starttls
+        smtp.connect(HOST, self.port)
+        self.assertEqual(smtp._host, HOST)
+        smtp.close()
+
 
 # Test server thread using the specified SMTP server class
 def debugging_server(serv, serv_evt, client_evt):