为什么我无法在 Python 中两次登录 imap 服务器

正如下面的错误消息所示，我无法登录，因为我处于 LOGOUT 状态而不是 NONAUTH 状态。如何从 LOGOUT 转到 NONAUTH？

下面的示例（显然下面的登录凭据是伪造的）

Python 2.7.3 (default, Aug  1 2012, 05:14:39)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import imaplib
>>> imap_server = imaplib.IMAP4_SSL("imap.gmail.com",993)
>>> imap_server.login('[email protected] /cdn-cgi/l/email-protection', 'mypassword')
('OK', ['[email protected] /cdn-cgi/l/email-protection Joe Smith authenticated (Success)'])
>>> imap_server.logout()
('BYE', ['LOGOUT Requested'])
>>> imap_server.login('[email protected] /cdn-cgi/l/email-protection', 'mypassword')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/imaplib.py", line 505, in login
    typ, dat = self._simple_command('LOGIN', user, self._quote(password))
  File "/usr/lib/python2.7/imaplib.py", line 1070, in _simple_command
    return self._command_complete(name, self._command(name, *args))
  File "/usr/lib/python2.7/imaplib.py", line 825, in _command
    ', '.join(Commands[name])))
imaplib.error: command LOGIN illegal in state LOGOUT, only allowed in states NONAUTH
>>> quit()

您尝试做的事情在 IMAP 中是非法的。如果你读完RFC 3501 https://www.rfc-editor.org/rfc/rfc3501，它明确定义了注销状态 https://www.rfc-editor.org/rfc/rfc3501#section-3.4作为一种无法返回的状态。您是否收到错误imaplib它本身，或者来自服务器，或者你真的很不幸，它会起作用并带你进入未定义行为的领域......答案是相同的：不要这样做。

因此，您必须创建与服务器的新连接才能再次登录：

>>> imap_server.logout()
('BYE', ['LOGOUT Requested'])
>>> imap_server = imaplib.IMAP4_SSL("imap.gmail.com",993)
>>> imap_server.login('[email protected] /cdn-cgi/l/email-protection', 'mypassword')
('OK', ['[email protected] /cdn-cgi/l/email-protection Joe Smith authenticated (Success)'])

（当然不必重新绑定同名imap_server到新的连接。）