pop3

• POP3

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Email - POP3 email services

1 Although most POP clients have an option to leave messages on the

server after downloading a copy of them, most e-mail clients using POP3

simply connect, retrieve all messages, store them on the client

device as new messages, delete them from the server, and then

disconnect


E-mail - POP3 email services


server after downloading a copy of them, most e-mail clients using POP3



disconnect


POP3

1 In computing, the 'Post Office Protocol' ('POP') is an application layer|

application-layer Internet standard protocol (computing)|protocol used by local e-mail clients to retrieve e-mail

from a remote mail server|server over a Internet protocol suite|TCP/IP connection. POP has been developed through several

versions, with version 3 ('POP3') being the current standard.


POP3

1 Virtually all modern e-mail clients and Server (computing)|servers support

POP3, and it along with IMAP (Internet Message Access Protocol) are the two

most prevalent Internet standard protocols for e-mail retrieval, with many

webmail service providers such as Google Mail, Microsoft Mail and Yahoo! Mail also

providing support for either IMAP or POP3 to allow mail to be downloaded.


POP3 - Overview

1 A POP3 server listens on List of TCP and UDP port numbers|well-known port 110. encryption|Encrypted communication for POP3 is either requested after protocol

initiation, using the STARTTLS|STLS command, if supported, or by POP3S, which connects to the server using

Transport Layer Security (TLS) or Secure Sockets Layer (SSL) on well-known TCP

port 995.


POP3 - History

1 POP3 originated with RFC 1081 (1988). Its current specification is

RFC 1939, updated with an extension mechanism, RFC 2449 and an

authentication mechanism in RFC 1734.


POP3 - History

1 POP3 clients support Simple Authentication and Security Layer|

SASL authentication methods via the AUTH extension


POP3 - Extensions

1 An extension mechanism was proposed in RFC 2449 to accommodate general extensions as well as announce in an

organized manner support for optional commands, such as TOP and UIDL. The

RFC did not intend to encourage extensions, and reaffirmed that the role of POP3 is to provide simple support for

mainly download-and-delete requirements of mailbox handling.


POP3 - STARTTLS

1 The STARTTLS extension allows the use of Transport Layer Security (TLS) or Secure Sockets Layer (SSL) to be

negotiated using the STLS command, on the standard POP3 port, rather

than an alternate. Some clients and servers instead use the alternate-port method, which uses TCP port

995 (POP3S).


POP3 - SDPS

1 Demon Internet introduced extensions to POP3 that allow multiple accounts per

domain, and has become known as Standard Dial-up POP3 Service

(SDPS).[http://e.demon.net/helpdesk/producthelp/mail/sdps-tech.html/ Demon Online Help Centre]. E.demon.net (2013-01-23). Retrieved on 2013-07-17. To access each

account, the username includes the hostname, as john@hostname or

john+hostname.


POP3 - Dialog example

1 POP3 servers without the optional APOP command expect the client to

log in with the USER and PASS commands:


POP3 - Related requests for comments (RFCs)

1 * RFC 5034 – The Post Office Protocol (POP3) Simple Authentication and

Security Layer (SASL) Authentication Mechanism


Yahoo! Mail - POP3

1 Users from countries where there is a web browser access restriction can get around it by using software that

simulates a POP3 server to which the email application connects, such as

YPOPs! and FreePOPs.


Yahoo! Mail - POP3

1 Another way of getting POP3 access without signing up for the paid mail plans is via Yahoo! Delivers, which sends the user promotional email

messages. According to the Yahoo! Mail help pages, Yahoo! offers POP

access to Yahoo! Mail as a free feature exclusively for Yahoo!

Delivers members. However, this applies only to users of Canadian

Yahoo Mail with @yahoo.ca extension of their mail.


Yahoo! Mail - POP3

1 As of October 2013, Yahoo provides paid subscribers POP3 access and forwarding.


RFC 2822 - POP3 email services


server after downloading a copy of them, most email clients using POP3



disconnect.


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