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gh-132796: Closes SMTP connection on 421 during data in sendmail #132797

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9 changes: 8 additions & 1 deletion Lib/smtplib.py
Original file line number Diff line number Diff line change
@@ -886,7 +886,14 @@ def sendmail(self, from_addr, to_addrs, msg, mail_options=(),
# the server refused all our recipients
self._rset()
raise SMTPRecipientsRefused(senderrs)
(code, resp) = self.data(msg)
try:
(code, resp) = self.data(msg)
except SMTPDataError as ex:
if ex.smtp_code == 421:
self.close()
else:
self._rset()
raise
if code != 250:
if code == 421:
self.close()
14 changes: 14 additions & 0 deletions Lib/test/test_smtplib.py
Original file line number Diff line number Diff line change
@@ -1259,6 +1259,10 @@ def test__rest_from_mail_cmd(self):
smtp.sendmail('John', 'Sally', 'test message')
self.assertIsNone(smtp.sock)

# The following 421 response tests for sendmail ensure that sendmail handles
# 421 respones correctly by closing the connection. sendmail has to take
# care of this, as it wraps a mail transaction for users.

# Issue 5713: make sure close, not rset, is called if we get a 421 error
def test_421_from_mail_cmd(self):
smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost',
@@ -1297,6 +1301,16 @@ def found_terminator(self):
self.assertIsNone(smtp.sock)
self.assertEqual(self.serv._SMTPchannel.rcpt_count, 0)

def test_421_during_data_cmd(self):
smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost',
timeout=support.LOOPBACK_TIMEOUT)
smtp.noop()
self.serv._SMTPchannel.data_response = '421 closing'
with self.assertRaises(smtplib.SMTPDataError):
smtp.sendmail('[email protected]', ['[email protected]'], 'test message')
self.assertIsNone(smtp.sock)
self.assertEqual(self.serv._SMTPchannel.rcpt_count, 0)

def test_smtputf8_NotSupportedError_if_no_server_support(self):
smtp = smtplib.SMTP(
HOST, self.port, local_hostname='localhost',
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Improve handling of 421 SMTP responses in :meth:`smtplib.SMTP.sendmail` by
covering a previously missing case in which 421 occurs while sending a DATA
command.