Oh, sorry, my bad. That was precisely what commit 48ed88a93bb0bbeaae9a4cfaa533e4edf13bcb51 changed. The problem with running with -R still happens:

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ERROR: test_name_field_not_included_in_envelop_addresses (test.test_smtplib.SMTPSimTests)
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Traceback (most recent call last):
  File "/Users/pgalindo3/cpython/Lib/test/test_smtplib.py", line 1100, in test_name_field_not_included_in_envelop_addresses
    self.assertDictEqual(smtp.send_message(message), {})
  File "/Users/pgalindo3/cpython/Lib/smtplib.py", line 967, in send_message
    rcpt_options)
  File "/Users/pgalindo3/cpython/Lib/smtplib.py", line 861, in sendmail
    (code, resp) = self.mail(from_addr, esmtp_opts)
  File "/Users/pgalindo3/cpython/Lib/smtplib.py", line 532, in mail
    'SMTPUTF8 not supported by server')
smtplib.SMTPNotSupportedError: SMTPUTF8 not supported by server

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Ran 60 tests in 1.365s

FAILED (errors=7)
Warning -- threading._dangling was modified by test_smtplib
  Before: <_weakrefset.WeakSet object at 0x10f445e90>
  After:  <_weakrefset.WeakSet object at 0x10fe75ad0>
test test_smtplib failed
test_smtplib failed

== Tests result: FAILURE ==

1 test failed:
    test_smtplib

Total duration: 2 sec 920 ms
Tests result: FAILURE