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

Without this reset, starttls would fail if a connect/starttls was done after a
quit, because smtplib assumed the existing value of emspt_features was
accurate, but it gets reset when starttls completes (and the new value does
not contain the starttls capability, since tls is already started at that
point).  (There may be additional places where this lack of reset was an
issue as well.)

Patch by Milan Oberkirch.

Lib/smtplib.py

@@ -866,6 +866,10 @@ 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

@@ -858,6 +858,21 @@ class SMTPSimTests(unittest.TestCase):
             self.assertIn(sim_auth_login_password, 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

@@ -27,6 +27,10 @@ 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 #22185: Fix an occasional RuntimeError in threading.Condition.wait()
   caused by mutation of the waiters queue without holding the lock.  Patch
   by Doug Zongker.