UnicodeDecodeError: 'ascii' codec can't decode byte 0xd8 in position 54: ordinal not in range(128) #120

2017-03-08 21:35:42,844.844 ERROR socket - _log_error: fd:124:error address=('fmx.freemail.hu', 25) args=(1, u'[SSL: ...l.c:590)') message='[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)'
Traceback (most recent call last):
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/gevent/greenlet.py", line 536, in run
    result = self._run(*self.args, **self.kwargs)
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/slimta/relay/smtp/client.py", line 290, in _run
    relay_error = SmtpRelayError.factory(reply)
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/slimta/relay/smtp/__init__.py", line 50, in factory
    return SmtpTransientRelayError(reply)
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/slimta/relay/smtp/__init__.py", line 56, in __init__
    super(SmtpTransientRelayError, self).__init__('Transient', reply)
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/slimta/relay/smtp/__init__.py", line 42, in __init__
    type, command.decode('ascii'), str(reply))
  File "/root/venv_cpython_2017/local/lib/python2.7/site-packages/slimta/smtp/reply.py", line 114, in __bytes__
    self.message.encode('utf-8')))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xd8 in position 54: ordinal not in range(128)
Wed Mar  8 21:35:42 2017 <SmtpRelayClient at 0x2acfcff16d70> failed with UnicodeDecodeError