20.12. 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
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 poplib.POP3(host[, port[, timeout]])
- 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. The optional timeout parameter specifies a timeout in seconds for the
connection attempt (if not specified, the global default timeout setting will
class poplib.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.
One exception is defined as an attribute of the poplib module:
- Exception raised on any errors from this module (errors from socket
module are not caught). The reason for the exception is passed to the
constructor as a string.
- 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.
20.12.1. 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:
- Set the instance’s debugging level. This controls the amount of debugging
output printed. The default, 0, produces no debugging output. A value of
1 produces a moderate amount of debugging output, generally a single line
per request. A value of 2 or higher produces the maximum amount of
debugging output, logging each line sent and received on the control connection.
- Returns the greeting string sent by the POP3 server.
- Send user command, response should indicate that a password is required.
- Send password, response includes message count and mailbox size. Note: the
mailbox on the server is locked until quit() is called.
- Use the more secure APOP authentication to log into the POP3 server.
- Use RPOP authentication (similar to UNIX r-commands) to log into POP3 server.
- Get mailbox status. The result is a tuple of 2 integers: (message count,
- Request message list, result is in the form (response, ['mesg_num octets',
...], octets). If which is set, it is the message to list.
- Retrieve whole message number which, and set its seen flag. Result is in form
(response, ['line', ...], octets).
- Flag message number which for deletion. On most servers deletions are not
actually performed until QUIT (the major exception is Eudora QPOP, which
deliberately violates the RFCs by doing pending deletes on any disconnect).
- Remove any deletion marks for the mailbox.
- Do nothing. Might be used as a keep-alive.
- Signoff: commit changes, unlock mailbox, drop connection.
Retrieves the message header plus howmuch lines of the message after the
header of message number which. Result is in form (response, ['line', ...],
The POP3 TOP command this method uses, unlike the RETR command, doesn’t set the
message’s seen flag; unfortunately, TOP is poorly specified in the RFCs and is
frequently broken in off-brand servers. Test this method by hand against the
POP3 servers you will use before trusting it.
- Return message digest (unique id) list. If which is specified, result contains
the unique id for that message in the form 'response mesgnum uid, otherwise
result is list (response, ['mesgnum uid', ...], octets).
Instances of POP3_SSL have no additional methods. The interface of this
subclass is identical to its parent.
20.12.2. POP3 Example
Here is a minimal example (without error checking) that opens a mailbox and
retrieves and prints all messages:
import getpass, poplib
M = poplib.POP3('localhost')
numMessages = len(M.list())
for i in range(numMessages):
for j in M.retr(i+1):
At the end of the module, there is a test section that contains a more extensive
example of usage.