flask的sendemail在开发环境下好用放到服务器上就瘫痪了是为啥

在windows上开发，服务器是linux
原环境是3.6，服务器上是3.5，跟这个有关系？
其他部分代码啥都没变一个好用一个就不好用
经过错误排查，版本跟这个没关系
但是为啥一放到服务器上就出错啊啊啊啊
求大佬解答，已抓狂
这是错误提示

Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "./app/email.py", line 9, in send_async_email
    mail.send(msg)
  File "/home/ubuntu/www/moji/venv/lib/python3.5/site-packages/flask_mail.py", line 491, in send
    with self.connect() as connection:
  File "/home/ubuntu/www/moji/venv/lib/python3.5/site-packages/flask_mail.py", line 144, in __enter__
    self.host = self.configure_host()
  File "/home/ubuntu/www/moji/venv/lib/python3.5/site-packages/flask_mail.py", line 158, in configure_host
    host = smtplib.SMTP(self.mail.server, self.mail.port)
  File "/usr/lib/python3.5/smtplib.py", line 251, in __init__
    (code, msg) = self.connect(host, port)
  File "/usr/lib/python3.5/smtplib.py", line 335, in connect
    self.sock = self._get_socket(host, port, self.timeout)
  File "/usr/lib/python3.5/smtplib.py", line 306, in _get_socket
    self.source_address)
  File "/usr/lib/python3.5/socket.py", line 711, in create_connection
    raise err
  File "/usr/lib/python3.5/socket.py", line 702, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused