在 Linux 但不是 Windows 上连接到 SMTP 服务器失败

在 python 脚本中，我有以下内容：

with smtplib.SMTP_SSL(sender_server, 465, context=context) as server:
    server.login(sender_email, sender_password)
    server.sendmail(
        sender_email, email, message.as_string()
    )

在我编写脚本的 Windows 机器上，一切都按预期进行，电子邮件的发送和交付没有问题。但是，当我尝试在 Linux VPS 上运行相同的代码时，每次都会抛出 TimeoutError。

Traceback (most recent call last):
  File "script.py", line 151, in <module>
    with smtplib.SMTP_SSL(sender_server, 465, context=context) as server:
  File "/usr/lib/python3.6/smtplib.py", line 1031, in __init__
    source_address)
  File "/usr/lib/python3.6/smtplib.py", line 251, in __init__
    (code, msg) = self.connect(host, port)
  File "/usr/lib/python3.6/smtplib.py", line 336, in connect
    self.sock = self._get_socket(host, port, self.timeout)
  File "/usr/lib/python3.6/smtplib.py", line 1037, in _get_socket
    self.source_address)
  File "/usr/lib/python3.6/socket.py", line 724, in create_connection
    raise err
  File "/usr/lib/python3.6/socket.py", line 713, in create_connection
    sock.connect(sa)
TimeoutError: [Errno 110] Connection timed out

什么可能导致这种差异？我的谷歌搜索并没有产生多少成果，但也许我只是在搜索错误的术语。