# 18.10 `poplib` -- POP3 protocol client

This module defines a class, `POP3`, which encapsulates a connection to a POP3 server and implements the protocol as defined in RFC 1725. The `POP3` class supports both the minimal and optional command sets. Additionally, this module provides a class `POP3_SSL`, which provides support for connecting to POP3 servers that use SSL as an underlying protocol layer.

Note that POP3, though widely supported, is obsolescent. The implementation quality of POP3 servers varies widely, and too many are quite poor. If your mailserver supports IMAP, you would be better off using the ``imaplib`.`IMAP4`` class, as IMAP servers tend to be better implemented.

A single class is provided by the `poplib` module:

class `POP3`( | host[, port])

  This class implements the actual POP3 protocol. The connection is created when the instance is initialized. If port is omitted, the standard POP3 port (110) is used.

class `POP3_SSL`( | host[, port[, keyfile[, certfile]]])

  This is a subclass of `POP3` that connects to the server over an SSL encrypted socket. If port is not specified, 995, the standard POP3-over-SSL port is used. keyfile and certfile are also optional - they can contain a PEM formatted private key and certificate chain file for the SSL connection.

  New in version 2.4.

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

exception `error_proto`
  Exception raised on any errors. The reason for the exception is passed to the constructor as a string.

See Also:

Module `imaplib`:
  The standard Python IMAP module.

Frequently Asked Questions About Fetchmail
  The FAQ for the fetchmail POP/IMAP client collects information on POP3 server variations and RFC noncompliance that may be useful if you need to write an application based on the POP protocol.