Merge #22215: have the smtplib 'quit' command reset the state.

Lib/smtplib.py

@@ -891,6 +891,10 @@ class SMTP:
     def quit(self):
         """Terminate the SMTP session."""
         res = self.docmd("quit")
+        # A new EHLO is required after reconnecting with connect()
+        self.ehlo_resp = self.helo_resp = None
+        self.esmtp_features = {}
+        self.does_esmtp = False
         self.close()
         return res
 

Lib/test/test_smtplib.py

@@ -876,6 +876,21 @@ class SMTPSimTests(unittest.TestCase):
                               str(err))
         smtp.close()
 
+    def test_quit_resets_greeting(self):
+        smtp = smtplib.SMTP(HOST, self.port,
+                            local_hostname='localhost',
+                            timeout=15)
+        code, message = smtp.ehlo()
+        self.assertEqual(code, 250)
+        self.assertIn('size', smtp.esmtp_features)
+        smtp.quit()
+        self.assertNotIn('size', smtp.esmtp_features)
+        smtp.connect(HOST, self.port)
+        self.assertNotIn('size', smtp.esmtp_features)
+        smtp.ehlo_or_helo_if_needed()
+        self.assertIn('size', smtp.esmtp_features)
+        smtp.quit()
+
     def test_with_statement(self):
         with smtplib.SMTP(HOST, self.port) as smtp:
             code, message = smtp.noop()

Misc/NEWS

@@ -124,6 +124,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #22216: smtplib now resets its state more completely after a quit.  The
+  most obvious consequence of the previous behavior was a STARTTLS failure
+  during a connect/starttls/quit/connect/starttls sequence.
+
 - Issue #22098: ctypes' BigEndianStructure and LittleEndianStructure now
   define an empty __slots__ so that subclasses don't always get an instance
   dict.  Patch by Claudiu Popa.