设置了SMTP交易后通知，每次交易后会出现这个错误:
Traceback (most recent call last):
File "C:\veighna_studio\lib\threading.py", line 1016, in _bootstrap_inner
self.run()
File "C:\veighna_studio\lib\threading.py", line 953, in run
self._target(*self._args, **self._kwargs)
File "C:\veighna_studio\lib\site-packages\vnpy\trader\engine.py", line 655, in run
smtp.login(
File "C:\veighna_studio\lib\smtplib.py", line 714, in login
self.ehlo_or_helo_if_needed()
File "C:\veighna_studio\lib\smtplib.py", line 611, in ehlo_or_helo_if_needed
if not (200 <= self.ehlo()[0] <= 299):
File "C:\veighna_studio\lib\smtplib.py", line 451, in ehlo
self.putcmd(self.ehlo_msg, name or self.local_hostname)
File "C:\veighna_studio\lib\smtplib.py", line 378, in putcmd
self.send(f'{s}{CRLF}')
File "C:\veighna_studio\lib\smtplib.py", line 365, in send
raise SMTPServerDisconnected('please run connect() first')
smtplib.SMTPServerDisconnected: please run connect() first
请问是什么问题？
