poplib —- POP3 protocol client

Source code:Lib/poplib.py

This module defines a class, POP3, which encapsulates a connection to aPOP3 server and implements the protocol as defined in RFC 1939. ThePOP3 class supports both the minimal and optional command sets fromRFC 1939. The POP3 class also supports the STLS command introducedin RFC 2595 to enable encrypted communication on an already established connection.

Additionally, this module provides a class POP3_SSL, which providessupport for connecting to POP3 servers that use SSL as an underlying protocollayer.

Note that POP3, though widely supported, is obsolescent. The implementationquality of POP3 servers varies widely, and too many are quite poor. If yourmailserver supports IMAP, you would be better off using theimaplib.IMAP4 class, as IMAP servers tend to be better implemented.

The poplib module provides two classes:

  • class poplib.POP3(host, port=POP3_PORT[, timeout])
  • This class implements the actual POP3 protocol. The connection is created whenthe instance is initialized. If port is omitted, the standard POP3 port (110)is used. The optional timeout parameter specifies a timeout in seconds for theconnection attempt (if not specified, the global default timeout setting willbe used).
  • class poplib.POP3SSL(_host, port=POP3_SSL_PORT, keyfile=None, certfile=None, timeout=None, context=None)
  • This is a subclass of POP3 that connects to the server over an SSLencrypted socket. If port is not specified, 995, the standard POP3-over-SSLport is used. timeout works as in the POP3 constructor.context is an optional ssl.SSLContext object which allowsbundling SSL configuration options, certificates and private keys into asingle (potentially long-lived) structure. Please read Security considerationsfor best practices.

keyfile and certfile are a legacy alternative to context - they canpoint to PEM-formatted private key and certificate chain files,respectively, for the SSL connection.

在 3.2 版更改: context parameter added.

在 3.4 版更改: The class now supports hostname check withssl.SSLContext.check_hostname and Server Name Indication (seessl.HAS_SNI).

3.6 版后已移除: keyfile and certfile are deprecated in favor of context.Please use ssl.SSLContext.load_cert_chain() instead, or letssl.create_default_context() select the system's trusted CAcertificates for you.

One exception is defined as an attribute of the poplib module:

  • exception poplib.error_proto
  • Exception raised on any errors from this module (errors from socketmodule are not caught). The reason for the exception is passed to theconstructor as a string.

参见

  • Module imaplib

  • The standard Python IMAP module.

  • Frequently Asked Questions About Fetchmail

  • The FAQ for the fetchmail POP/IMAP client collects information onPOP3 server variations and RFC noncompliance that may be useful if you need towrite an application based on the POP protocol.

POP3 Objects

All POP3 commands are represented by methods of the same name, in lower-case;most return the response text sent by the server.

An POP3 instance has the following methods:

  • POP3.setdebuglevel(_level)
  • Set the instance's debugging level. This controls the amount of debuggingoutput printed. The default, 0, produces no debugging output. A value of1 produces a moderate amount of debugging output, generally a single lineper request. A value of 2 or higher produces the maximum amount ofdebugging output, logging each line sent and received on the control connection.
  • POP3.getwelcome()
  • Returns the greeting string sent by the POP3 server.
  • POP3.capa()
  • Query the server's capabilities as specified in RFC 2449.Returns a dictionary in the form {'name': ['param'…]}.

3.4 新版功能.

  • POP3.user(username)
  • Send user command, response should indicate that a password is required.
  • POP3.pass(_password)
  • Send password, response includes message count and mailbox size. Note: themailbox on the server is locked until quit() is called.
  • POP3.apop(user, secret)
  • Use the more secure APOP authentication to log into the POP3 server.
  • POP3.rpop(user)
  • Use RPOP authentication (similar to UNIX r-commands) to log into POP3 server.
  • POP3.stat()
  • Get mailbox status. The result is a tuple of 2 integers: (message count,mailbox size).
  • POP3.list([which])
  • Request message list, result is in the form (response, ['mesgnum octets',…], octets). If _which is set, it is the message to list.
  • POP3.retr(which)
  • Retrieve whole message number which, and set its seen flag. Result is in form(response, ['line', …], octets).
  • POP3.dele(which)
  • Flag message number which for deletion. On most servers deletions are notactually performed until QUIT (the major exception is Eudora QPOP, whichdeliberately violates the RFCs by doing pending deletes on any disconnect).
  • POP3.rset()
  • Remove any deletion marks for the mailbox.
  • POP3.noop()
  • Do nothing. Might be used as a keep-alive.
  • POP3.quit()
  • Signoff: commit changes, unlock mailbox, drop connection.
  • POP3.top(which, howmuch)
  • Retrieves the message header plus howmuch lines of the message after theheader of message number which. Result is in form (response, ['line', …],octets).

The POP3 TOP command this method uses, unlike the RETR command, doesn't set themessage's seen flag; unfortunately, TOP is poorly specified in the RFCs and isfrequently broken in off-brand servers. Test this method by hand against thePOP3 servers you will use before trusting it.

  • POP3.uidl(which=None)
  • Return message digest (unique id) list. If which is specified, result containsthe unique id for that message in the form 'response mesgnum uid, otherwiseresult is list (response, ['mesgnum uid', …], octets).
  • POP3.utf8()
  • Try to switch to UTF-8 mode. Returns the server response if successful,raises error_proto if not. Specified in RFC 6856.

3.5 新版功能.

  • POP3.stls(context=None)
  • Start a TLS session on the active connection as specified in RFC 2595.This is only allowed before user authentication

context parameter is a ssl.SSLContext object which allowsbundling SSL configuration options, certificates and private keys intoa single (potentially long-lived) structure. Please read Security considerationsfor best practices.

This method supports hostname checking viassl.SSLContext.check_hostname and Server Name Indication (seessl.HAS_SNI).

3.4 新版功能.

Instances of POP3_SSL have no additional methods. The interface of thissubclass is identical to its parent.

POP3 Example

Here is a minimal example (without error checking) that opens a mailbox andretrieves and prints all messages:

  1. import getpass, poplib
  2.  
  3. M = poplib.POP3('localhost')
  4. M.user(getpass.getuser())
  5. M.pass_(getpass.getpass())
  6. numMessages = len(M.list()[1])
  7. for i in range(numMessages):
  8.     for j in M.retr(i+1)[1]:
  9.         print(j)

At the end of the module, there is a test section that contains a more extensiveexample of usage.