gh-48392: Fix smtplib.SMTP.close() not resetting the EHLO state

Lib/smtplib.py

@@ -989,6 +989,11 @@ def send_message(self, msg, from_addr=None, to_addrs=None,
 
     def close(self):
         """Close the connection to the SMTP server."""
+        # A new EHLO is required after reconnecting with connect()
+        self.ehlo_resp = self.helo_resp = None
+        self.esmtp_features = {}
+        self.does_esmtp = False
+
         try:
             file = self.file
             self.file = None
@@ -1003,10 +1008,6 @@ def close(self):
     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

@@ -1265,6 +1265,40 @@ def test_quit_resets_greeting(self):
         self.assertIn('size', smtp.esmtp_features)
         smtp.quit()
 
+    def test_close_resets_greeting(self):
+        smtp = smtplib.SMTP(HOST, self.port,
+                            local_hostname='localhost',
+                            timeout=support.LOOPBACK_TIMEOUT)
+        code, _ = smtp.ehlo()
+        self.assertEqual(code, 250)
+        self.assertIn('size', smtp.esmtp_features)
+        smtp.close()
+        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_resets_greeting(self):
+        with smtplib.SMTP(HOST, self.port,
+                          local_hostname='localhost',
+                          timeout=support.LOOPBACK_TIMEOUT) as smtp:
+            smtp.ehlo()
+            self.assertIn('size', smtp.esmtp_features)
+
+        self.assertNotIn('size', smtp.esmtp_features)
+
+        msg = EmailMessage()
+        msg['From'] = 'test_from'
+        msg['To'] = 'test_to'
+        msg['Subject'] = 'test_subject'
+
+        smtp.connect(HOST, self.port)
+        smtp.send_message(msg)
+        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.d/next/Library/2026-11-03-15-04-43.gh-issue-48392.DNjjZT.rst

@@ -0,0 +1,3 @@
+Fix :meth:`!smtplib.SMTP.close` not resetting the EHLO state, so an
+:class:`!SMTP` object reconnected with :meth:`~smtplib.SMTP.connect` sent
+``MAIL FROM`` without a new EHLO.