'Regression test for #15042'

def test_recipient_without_domain(self):

    self.assertTrue(send_mail('Subject', 'Content', 'tester', ['django']))
    message = self.get_the_message()
    self.assertEqual(message.get('subject'), 'Subject')
    self.assertEqual(message.get('from'), 'tester')
    self.assertEqual(message.get('to'), 'django')
