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class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Extensions and specifications subsection</span> </button> <ul id="toc-Extensions_and_specifications-sublist" class="vector-toc-list"> <li id="toc-STARTTLS" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#STARTTLS"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>STARTTLS</span> </div> </a> <ul id="toc-STARTTLS-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-SDPS" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#SDPS"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>SDPS</span> </div> </a> <ul id="toc-SDPS-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Kerberized_Post_Office_Protocol" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Kerberized_Post_Office_Protocol"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Kerberized Post Office Protocol</span> </div> </a> <ul id="toc-Kerberized_Post_Office_Protocol-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Session_example" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Session_example"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Session example</span> </div> </a> <ul id="toc-Session_example-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Comparison_with_IMAP" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Comparison_with_IMAP"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Comparison with IMAP</span> </div> </a> <ul id="toc-Comparison_with_IMAP-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Related_requests_for_comments_(RFCs)" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Related_requests_for_comments_(RFCs)"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Related requests for comments (RFCs)</span> </div> </a> <ul id="toc-Related_requests_for_comments_(RFCs)-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div 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mw-first-heading"><span class="mw-page-title-main">Post Office Protocol</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 33 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-33" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">33 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%A8%D8%B1%D9%88%D8%AA%D9%88%D9%83%D9%88%D9%84_%D9%85%D9%83%D8%AA%D8%A8_%D8%A7%D9%84%D8%A8%D8%B1%D9%8A%D8%AF" title="بروتوكول مكتب البريد – Arabic" lang="ar" hreflang="ar" data-title="بروتوكول مكتب البريد" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Asturian" lang="ast" hreflang="ast" data-title="Post Office Protocol" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/POP" title="POP – Belarusian" lang="be" hreflang="be" data-title="POP" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Bulgarian" lang="bg" hreflang="bg" data-title="Post Office Protocol" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Bosnian" lang="bs" hreflang="bs" data-title="Post Office Protocol" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Catalan" lang="ca" hreflang="ca" data-title="Post Office Protocol" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Chuvash" lang="cv" hreflang="cv" data-title="Post Office Protocol" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Czech" lang="cs" hreflang="cs" data-title="Post Office Protocol" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – German" lang="de" hreflang="de" data-title="Post Office Protocol" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Postkontoriprotokoll" title="Postkontoriprotokoll – Estonian" lang="et" hreflang="et" data-title="Postkontoriprotokoll" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Greek" lang="el" hreflang="el" data-title="Post Office Protocol" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Protocolo_de_oficina_de_correo" title="Protocolo de oficina de correo – Spanish" lang="es" hreflang="es" data-title="Protocolo de oficina de correo" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/POP" title="POP – Basque" lang="eu" hreflang="eu" data-title="POP" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%BE%D8%A7%D9%BE_(%D9%BE%D8%B1%D9%88%D8%AA%DA%A9%D9%84)" title="پاپ (پروتکل) – Persian" lang="fa" hreflang="fa" data-title="پاپ (پروتکل)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – French" lang="fr" hreflang="fr" data-title="Post Office Protocol" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%8F%AC%EC%8A%A4%ED%8A%B8_%EC%98%A4%ED%94%BC%EC%8A%A4_%ED%94%84%EB%A1%9C%ED%86%A0%EC%BD%9C" title="포스트 오피스 프로토콜 – Korean" lang="ko" hreflang="ko" data-title="포스트 오피스 프로토콜" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Italian" lang="it" hreflang="it" data-title="Post Office Protocol" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Hebrew" lang="he" hreflang="he" data-title="Post Office Protocol" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Luxembourgish" lang="lb" hreflang="lb" data-title="Post Office Protocol" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Macedonian" lang="mk" hreflang="mk" data-title="Post Office Protocol" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Protokol_Pejabat_Pos" title="Protokol Pejabat Pos – Malay" lang="ms" hreflang="ms" data-title="Protokol Pejabat Pos" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Post_office_protocol" title="Post office protocol – Dutch" lang="nl" hreflang="nl" data-title="Post office protocol" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Japanese" lang="ja" hreflang="ja" data-title="Post Office Protocol" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Portuguese" lang="pt" hreflang="pt" data-title="Post Office Protocol" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Simple English" lang="en-simple" hreflang="en-simple" data-title="Post Office Protocol" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Slovak" lang="sk" hreflang="sk" data-title="Post Office Protocol" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/POP_(protokol)" title="POP (protokol) – Serbian" lang="sr" hreflang="sr" data-title="POP (protokol)" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Post Office Protocol" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%9E%E0%B9%87%E0%B8%AD%E0%B8%9B" title="พ็อป – Thai" lang="th" hreflang="th" data-title="พ็อป" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Ukrainian" lang="uk" hreflang="uk" data-title="Post Office Protocol" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Vietnamese" lang="vi" hreflang="vi" data-title="Post Office Protocol" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-yo mw-list-item"><a href="https://yo.wikipedia.org/wiki/Post_Office_Protocol" title="Post Office Protocol – Yoruba" lang="yo" hreflang="yo" data-title="Post Office Protocol" data-language-autonym="Yorùbá" data-language-local-name="Yoruba" class="interlanguage-link-target"><span>Yorùbá</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E9%83%B5%E5%B1%80%E5%8D%94%E5%AE%9A" title="郵局協定 – Chinese" lang="zh" hreflang="zh" data-title="郵局協定" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q1268005#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div 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screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar nomobile nowraplinks hlist"><tbody><tr><th class="sidebar-title"><a href="/wiki/Internet_protocol_suite" title="Internet protocol suite">Internet protocol suite</a></th></tr><tr><th class="sidebar-heading"> <a href="/wiki/Application_layer" title="Application layer">Application layer</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Border_Gateway_Protocol" title="Border Gateway Protocol">BGP</a></li> <li><a href="/wiki/Dynamic_Host_Configuration_Protocol" title="Dynamic Host Configuration Protocol">DHCP</a> (<a href="/wiki/DHCPv6" title="DHCPv6">v6</a>)</li> <li><a href="/wiki/Domain_Name_System" title="Domain Name System">DNS</a></li> <li><a href="/wiki/File_Transfer_Protocol" title="File Transfer Protocol">FTP</a></li> <li><a href="/wiki/HTTP" title="HTTP">HTTP</a> (<a href="/wiki/HTTP/3" title="HTTP/3">HTTP/3</a>)</li> <li><a href="/wiki/HTTPS" title="HTTPS">HTTPS</a></li> <li><a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">IMAP</a></li> <li><a href="/wiki/IRC" title="IRC">IRC</a></li> <li><a href="/wiki/Lightweight_Directory_Access_Protocol" title="Lightweight Directory Access Protocol">LDAP</a></li> <li><a href="/wiki/Media_Gateway_Control_Protocol" title="Media Gateway Control Protocol">MGCP</a></li> <li><a href="/wiki/MQTT" title="MQTT">MQTT</a></li> <li><a href="/wiki/Network_News_Transfer_Protocol" title="Network News Transfer Protocol">NNTP</a></li> <li><a href="/wiki/Network_Time_Protocol" title="Network Time Protocol">NTP</a></li> <li><a href="/wiki/Open_Shortest_Path_First" title="Open Shortest Path First">OSPF</a></li> <li><a class="mw-selflink selflink">POP</a></li> <li><a href="/wiki/Precision_Time_Protocol" title="Precision Time Protocol">PTP</a></li> <li><a href="/wiki/Open_Network_Computing_Remote_Procedure_Call" class="mw-redirect" title="Open Network Computing Remote Procedure Call">ONC/RPC</a></li> <li><a href="/wiki/Real-time_Transport_Protocol" title="Real-time Transport Protocol">RTP</a></li> <li><a href="/wiki/Real-Time_Streaming_Protocol" title="Real-Time Streaming Protocol">RTSP</a></li> <li><a href="/wiki/Routing_Information_Protocol" title="Routing Information Protocol">RIP</a></li> <li><a href="/wiki/Session_Initiation_Protocol" title="Session Initiation Protocol">SIP</a></li> <li><a href="/wiki/Simple_Mail_Transfer_Protocol" title="Simple Mail Transfer Protocol">SMTP</a></li> <li><a href="/wiki/Simple_Network_Management_Protocol" title="Simple Network Management Protocol">SNMP</a></li> <li><a href="/wiki/Secure_Shell" title="Secure Shell">SSH</a></li> <li><a href="/wiki/Telnet" title="Telnet">Telnet</a></li> <li><a href="/wiki/Transport_Layer_Security" title="Transport Layer Security">TLS/SSL</a></li> <li><a href="/wiki/XMPP" title="XMPP">XMPP</a></li> <li><a href="/wiki/Category:Application_layer_protocols" title="Category:Application layer protocols"><i>more...</i></a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/Transport_layer" title="Transport layer">Transport layer</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Transmission_Control_Protocol" title="Transmission Control Protocol">TCP</a></li> <li><a href="/wiki/User_Datagram_Protocol" title="User Datagram Protocol">UDP</a></li> <li><a href="/wiki/Datagram_Congestion_Control_Protocol" title="Datagram Congestion Control Protocol">DCCP</a></li> <li><a href="/wiki/Stream_Control_Transmission_Protocol" title="Stream Control Transmission Protocol">SCTP</a></li> <li><a href="/wiki/Resource_Reservation_Protocol" title="Resource Reservation Protocol">RSVP</a></li> <li><a href="/wiki/QUIC" title="QUIC">QUIC</a></li> <li><a href="/wiki/Category:Transport_layer_protocols" title="Category:Transport layer protocols"><i>more...</i></a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/Internet_layer" title="Internet layer">Internet layer</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Internet_Protocol" title="Internet Protocol">IP</a> <ul><li><a href="/wiki/IPv4" title="IPv4">v4</a></li> <li><a href="/wiki/IPv6" title="IPv6">v6</a></li></ul></li> <li><a href="/wiki/Internet_Control_Message_Protocol" title="Internet Control Message Protocol">ICMP</a> (<a href="/wiki/ICMPv6" title="ICMPv6">v6</a>)</li> <li><a href="/wiki/Neighbor_Discovery_Protocol" title="Neighbor Discovery Protocol">NDP</a></li> <li><a href="/wiki/Explicit_Congestion_Notification" title="Explicit Congestion Notification">ECN</a></li> <li><a href="/wiki/Internet_Group_Management_Protocol" title="Internet Group Management Protocol">IGMP</a></li> <li><a href="/wiki/IPsec" title="IPsec">IPsec</a></li> <li><a href="/wiki/Category:Internet_layer_protocols" title="Category:Internet layer protocols"><i>more...</i></a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/Link_layer" title="Link layer">Link layer</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Address_Resolution_Protocol" title="Address Resolution Protocol">ARP</a></li> <li><a href="/wiki/Tunneling_protocol" title="Tunneling protocol">Tunnels</a></li> <li><a href="/wiki/Point-to-Point_Protocol" title="Point-to-Point Protocol">PPP</a></li> <li><a href="/wiki/Medium_access_control" title="Medium access control">MAC</a></li> <li><a href="/wiki/Category:Link_protocols" title="Category:Link protocols"><i>more...</i></a></li></ul></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Internet_protocol_suite" title="Template:Internet protocol suite"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Internet_protocol_suite" title="Template talk:Internet protocol suite"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Internet_protocol_suite" title="Special:EditPage/Template:Internet protocol suite"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p>In computing, the <b>Post Office Protocol</b> (<b>POP</b>) is an <a href="/wiki/Application_layer" title="Application layer">application-layer</a> <a href="/wiki/Internet_standard" class="mw-redirect" title="Internet standard">Internet standard</a> <a href="/wiki/Protocol_(computing)" class="mw-redirect" title="Protocol (computing)">protocol</a> used by <a href="/wiki/E-mail_client" class="mw-redirect" title="E-mail client">e-mail clients</a> to retrieve <a href="/wiki/E-mail" class="mw-redirect" title="E-mail">e-mail</a> from a mail server.<sup id="cite_ref-Network+_Guide_to_Networks_1-0" class="reference"><a href="#cite_note-Network+_Guide_to_Networks-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Today, POP version 3 (<b>POP3</b>) is the most commonly used version. Together with <a href="/wiki/IMAP" class="mw-redirect" title="IMAP">IMAP</a>, it is one of the most common protocols for email retrieval. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Purpose">Purpose</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=1" title="Edit section: Purpose"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Post Office Protocol provides access via an <a href="/wiki/Internet_Protocol" title="Internet Protocol">Internet Protocol</a> (IP) network for a user client application to a mailbox (<i>maildrop</i>) maintained on a mail server. The protocol supports list, retrieve and delete operations for messages. POP3 clients connect, retrieve all messages, store them on the client computer, and finally delete them from the server.<sup id="cite_ref-Windows_to_Linux_2-0" class="reference"><a href="#cite_note-Windows_to_Linux-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> This design of POP and its procedures was driven by the need of users having only temporary Internet connections, such as <a href="/wiki/Dial-up_Internet_access" title="Dial-up Internet access">dial-up access</a>, allowing these users to retrieve e-mail when connected, and subsequently to view and manipulate the retrieved messages when offline. </p><p>POP3 clients also have an option to leave mail on the server after retrieval, and in this mode of operation, clients will only download new messages which are identified by using the UIDL command (unique-id list). By contrast, the <a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">Internet Message Access Protocol</a> (IMAP) was designed to normally leave all messages on the server to permit management with multiple client applications, and to support both connected (<i>online</i>) and disconnected (<i>offline</i>) modes of operation. </p><p>A POP3 server listens on TCP <a href="/wiki/List_of_TCP_and_UDP_port_numbers#Well-known_ports" title="List of TCP and UDP port numbers">well-known port number</a> 110 for service requests. <a href="/wiki/Secure_communication" title="Secure communication">Encrypted communication</a> for POP3 is either requested after protocol initiation, using the <a href="/wiki/STARTTLS" class="mw-redirect" title="STARTTLS">STLS</a> command, if supported, or by POP3S, which connects to the server using <a href="/wiki/Transport_Layer_Security" title="Transport Layer Security">Transport Layer Security</a> (TLS) or <a href="/wiki/Secure_Sockets_Layer" class="mw-redirect" title="Secure Sockets Layer">Secure Sockets Layer</a> (SSL) on well-known <a href="/wiki/Transmission_Control_Protocol" title="Transmission Control Protocol">TCP</a> <a href="/wiki/TCP_port" class="mw-redirect" title="TCP port">port</a> number 995. </p><p>Messages available to the client are determined when a POP3 session opens the maildrop, and are identified by message-number local to that <a href="/wiki/Session_(computer_science)" title="Session (computer science)">session</a> or, optionally, by a unique identifier assigned to the message by the POP server. This unique identifier is permanent and unique to the maildrop and allows a client to access the same message in different POP sessions. Mail is retrieved and marked for deletion by the message-number. When the client exits the session, mail marked for deletion is removed from the maildrop. </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=2" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first version of the Post Office Protocol, POP1, was specified in RFC 918 (1984) by <a href="/wiki/Joyce_K._Reynolds" title="Joyce K. Reynolds">Joyce K. Reynolds</a>. POP2 was specified in RFC 937 (1985). </p><p>POP3 is the version in most common use. It originated with RFC 1081 (1988) but the most recent specification is RFC 1939, updated with an extension mechanism (RFC 2449) and an authentication mechanism in RFC 1734. This led to a number of POP implementations such as Pine, <a href="/wiki/POPmail" class="mw-redirect" title="POPmail">POPmail</a>, and other early mail clients. </p><p>While the original POP3 specification supported only an unencrypted USER/<a href="/wiki/Password" title="Password">PASS</a> <a href="/wiki/Login" title="Login">login</a> mechanism or Berkeley <a href="/wiki/Rlogin" class="mw-redirect" title="Rlogin">.rhosts</a> access control, today POP3 supports several <a href="/wiki/Authentication" title="Authentication">authentication</a> methods to provide varying levels of protection against illegitimate access to a user's e-mail. Most are provided by the POP3 extension mechanisms. POP3 clients support <a href="/wiki/Simple_Authentication_and_Security_Layer" title="Simple Authentication and Security Layer">SASL</a> authentication methods via the AUTH extension. <a href="/wiki/Massachusetts_Institute_of_Technology" title="Massachusetts Institute of Technology">MIT</a> <a href="/wiki/Project_Athena" title="Project Athena">Project Athena</a> also produced a <a href="/wiki/Kerberized" class="mw-redirect" title="Kerberized">Kerberized</a> version. RFC 1460 introduced APOP into the core protocol. APOP is a <a href="/wiki/Challenge%E2%80%93response" class="mw-redirect" title="Challenge–response">challenge–response</a> protocol which uses the <a href="/wiki/MD5" title="MD5">MD5</a> <a href="/wiki/Cryptographic_hash_function" title="Cryptographic hash function">hash function</a> in an attempt to avoid <a href="/wiki/Replay_attack" title="Replay attack">replay attacks</a> and disclosure of the <a href="/wiki/Shared_secret" title="Shared secret">shared secret</a>. Clients implementing APOP include <a href="/wiki/Mozilla_Thunderbird" title="Mozilla Thunderbird">Mozilla Thunderbird</a>, <a href="/wiki/Opera_Mail" title="Opera Mail">Opera Mail</a>, <a href="/wiki/Eudora_(email_client)" title="Eudora (email client)">Eudora</a>, <a href="/wiki/KMail" class="mw-redirect" title="KMail">KMail</a>, <a href="/wiki/Novell_Evolution" class="mw-redirect" title="Novell Evolution">Novell Evolution</a>, RimArts' <a href="/wiki/Becky!" title="Becky!">Becky!</a>,<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Windows_Live_Mail" title="Windows Live Mail">Windows Live Mail</a>, PowerMail, <a href="/wiki/Apple_Mail" title="Apple Mail">Apple Mail</a>, and <a href="/wiki/Mutt_(e-mail_client)" class="mw-redirect" title="Mutt (e-mail client)">Mutt</a>. RFC 1460 was obsoleted by RFC 1725, which was in turn obsoleted by RFC 1939. </p> <div class="mw-heading mw-heading3"><h3 id="POP4">POP4</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=3" title="Edit section: POP4"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>POP4 exists only as an informal proposal adding basic folder management, multipart message support, as well as message flag management to compete with IMAP; however, its development has not progressed since 2003.There are now two known POP4 server implementations. As of October 2013, the POP4.org domain and website are now hosted by simbey.com, which also runs the other POP4 <a rel="nofollow" class="external text" href="http://www.pop4.org/">server implementation.</a><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Extensions_and_specifications">Extensions and specifications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=4" title="Edit section: Extensions and specifications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>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. </p><p>The extensions are termed capabilities and are listed by the CAPA command. With the exception of APOP, the optional commands were included in the initial set of capabilities. Following the lead of ESMTP (RFC 5321), capabilities beginning with an X signify local capabilities. </p> <div class="mw-heading mw-heading3"><h3 id="STARTTLS">STARTTLS</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=5" title="Edit section: STARTTLS"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The STARTTLS extension allows the use of <a href="/wiki/Transport_Layer_Security" title="Transport Layer Security">Transport Layer Security</a> (TLS) or <a href="/wiki/Secure_Sockets_Layer" class="mw-redirect" title="Secure Sockets Layer">Secure Sockets Layer</a> (SSL) to be negotiated using the <i>STLS</i> 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). </p> <div class="mw-heading mw-heading3"><h3 id="SDPS">SDPS</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=6" title="Edit section: SDPS"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Demon_Internet" title="Demon Internet">Demon Internet</a> introduced extensions to POP3 that allow multiple accounts per domain, and has become known as <i>Standard Dial-up POP3 Service</i> (SDPS).<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> To access each account, the username includes the hostname, as <i>john@hostname</i> or <i>john+hostname</i>. </p><p>Google Apps uses the same method.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Kerberized_Post_Office_Protocol">Kerberized Post Office Protocol</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=7" title="Edit section: Kerberized Post Office Protocol"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Computing" title="Computing">computing</a>, local <a href="/wiki/E-mail_client" class="mw-redirect" title="E-mail client">e-mail clients</a> can use the <b>Kerberized Post Office Protocol</b> (<b>KPOP</b>), an <a href="/wiki/Application_layer" title="Application layer">application-layer</a> <a href="/wiki/Internet_standard" class="mw-redirect" title="Internet standard">Internet standard</a> <a href="/wiki/Protocol_(computing)" class="mw-redirect" title="Protocol (computing)">protocol</a>, to retrieve <a href="/wiki/E-mail" class="mw-redirect" title="E-mail">e-mail</a> from a remote <a href="/wiki/Mail_server" class="mw-redirect" title="Mail server">server</a> over a <a href="/wiki/Internet_protocol_suite" title="Internet protocol suite">TCP/IP</a> connection. The KPOP protocol is based on the POP3 protocol – differing in that it adds <a href="/wiki/Kerberos_(protocol)" title="Kerberos (protocol)">Kerberos</a> security and that it runs by default over <a href="/wiki/Transmission_Control_Protocol" title="Transmission Control Protocol">TCP</a> port number 1109 instead of 110. One mail server software implementation is found in the <a href="/wiki/Cyrus_IMAP_server" title="Cyrus IMAP server">Cyrus IMAP server</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Session_example">Session example</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=8" title="Edit section: Session example"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following POP3 session dialog is an example in RFC 1939:<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <pre><span style="color:blue;font-face=italic">S: <wait for connection on TCP port 110></span> C: <open connection> <span style="color:blue;">S: +OK POP3 server ready <1896.697170952@dbc.mtview.ca.us></span> C: APOP mrose c4c9334bac560ecc979e58001b3e22fb <span style="color:blue;">S: +OK mrose's maildrop has 2 messages (320 octets)</span> C: STAT <span style="color:blue;">S: +OK 2 320</span> C: LIST <span style="color:blue;">S: +OK 2 messages (320 octets)</span> <span style="color:blue;">S: 1 120</span> <span style="color:blue;">S: 2 200</span> <span style="color:blue;">S: .</span> C: RETR 1 <span style="color:blue;">S: +OK 120 octets</span> <span style="color:blue;">S: <the POP3 server sends message 1></span> <span style="color:blue;">S: .</span> C: DELE 1 <span style="color:blue;">S: +OK message 1 deleted</span> C: RETR 2 <span style="color:blue;">S: +OK 200 octets</span> <span style="color:blue;">S: <the POP3 server sends message 2></span> <span style="color:blue;">S: .</span> C: DELE 2 <span style="color:blue;">S: +OK message 2 deleted</span> C: QUIT <span style="color:blue;">S: +OK dewey POP3 server signing off (maildrop empty)</span> C: <close connection> <span style="color:blue;">S: <wait for next connection></span> </pre> <p>POP3 servers without the optional APOP command expect the client to log in with the USER and PASS commands: </p> <pre>C: USER mrose <span style="color:blue;">S: +OK User accepted</span> C: PASS tanstaaf <span style="color:blue;">S: +OK Pass accepted</span> </pre> <div class="mw-heading mw-heading2"><h2 id="Comparison_with_IMAP">Comparison with IMAP</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=9" title="Edit section: Comparison with IMAP"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">Internet Message Access Protocol</a> (IMAP) is an alternative and more recent mailbox access protocol. The highlights of differences are: </p> <ul><li>POP is a simpler protocol, making implementation easier.</li> <li>POP moves the message from the email server to the local computer, although there is usually an option in email clients to leave the messages on the email server as well. IMAP defaults to leaving the message on the email server, simply downloading a local copy.</li> <li>POP treats the mailbox as a single store, and has no concept of folders</li> <li>An IMAP client performs complex queries, asking the server for headers, or the bodies of specified messages, or to search for messages meeting certain criteria. Messages in the mail repository can be marked with various status flags (e.g. "deleted" or "answered") and they stay in the repository until explicitly removed by the user—which may not be until a later session. In short: IMAP is designed to permit manipulation of remote mailboxes as if they were local. Depending on the IMAP client implementation and the mail architecture desired by the system manager, the user may save messages directly on the client machine, or save them on the server, or be given the choice of doing either.</li> <li>POP provides a completely <i>static</i> view of the current state of the mailbox, and does not provide a mechanism to show any external changes in state <i>during</i> the session (the client must reconnect and re-authenticate to get an updated view).</li> <li>IMAP provides a <i>dynamic</i> view, and sends responses for external changes in state, including newly arrived messages, as well as changes made to the mailbox by other concurrently connected clients.</li> <li>POP can either retrieve an entire message with the RETR command, and for servers that support it, the headers, as well as a specified number of body lines can be accessed with the TOP command.</li> <li>IMAP allows clients to retrieve any of the individual <a href="/wiki/MIME" title="MIME">MIME</a> parts separately – for example, retrieving the plain text without retrieving attached files, or retrieving only one of many attached files.</li> <li>IMAP supports flags on the server to keep track of message state: for example, whether or not the message has been read, replied to, forwarded, or deleted.</li> <li>POP provides the ability to associate unique identifiers with each message for servers which support the UIDL command. This can be any string of standard visible (non-whitespace) 7-bit ASCII characters up to 70 characters.</li> <li>IMAP instead provides unique numerical identifiers for each message, local to each folder, in conjunction with a folder specific UIDVALIDITY number.</li> <li>The above two message identification methods (POP UIDL and IMAP UID) are not at all related unless a server implementation which supports both protocols purposely builds the POP3 UIDL string by combining the IMAP UID and UIDVALIDITY values.</li></ul> <div class="mw-heading mw-heading2"><h2 id="Related_requests_for_comments_(RFCs)"><span id="Related_requests_for_comments_.28RFCs.29"></span>Related requests for comments (RFCs)</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=10" title="Edit section: Related requests for comments (RFCs)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style>RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc918">918</a> – POST OFFICE PROTOCOL</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc937">937</a> – POST OFFICE PROTOCOL – VERSION 2</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc1081">1081</a> – Post Office Protocol – Version 3</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc1939">1939</a> – Post Office Protocol – Version 3 (STD 53)</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc1957">1957</a> – Some Observations on Implementations of the Post Office Protocol (POP3)</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc2195">2195</a> – IMAP/POP AUTHorize Extension for Simple Challenge/Response</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc2384">2384</a> – POP URL Scheme</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc2449">2449</a> – POP3 Extension Mechanism</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc2595">2595</a> – Using TLS with IMAP, POP3 and ACAP</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3206">3206</a> – The SYS and AUTH POP Response Codes</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc5034">5034</a> – The Post Office Protocol (POP3) Simple Authentication and Security Layer (SASL) Authentication Mechanism</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc8314">8314</a> – Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access</li></ul> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=11" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/List_of_mail_server_software" title="List of mail server software">List of mail server software</a></li> <li><a href="/wiki/Comparison_of_email_clients" title="Comparison of email clients">Comparison of email clients</a></li> <li><a href="/wiki/Comparison_of_mail_servers" title="Comparison of mail servers">Comparison of mail servers</a></li> <li><a href="/wiki/Email_encryption" title="Email encryption">Email encryption</a></li> <li><a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">Internet Message Access Protocol</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=12" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-Network+_Guide_to_Networks-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Network+_Guide_to_Networks_1-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDean2010" class="citation book cs1">Dean, Tamara (2010). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=UD0h_GqgbHgC&q=network%2B+guide+to+networks"><i>Network+ Guide to Networks</i></a>. Delmar. p. 519. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1423902454" title="Special:BookSources/978-1423902454"><bdi>978-1423902454</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Network%2B+Guide+to+Networks&rft.pages=519&rft.pub=Delmar&rft.date=2010&rft.isbn=978-1423902454&rft.aulast=Dean&rft.aufirst=Tamara&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DUD0h_GqgbHgC%26q%3Dnetwork%252B%2Bguide%2Bto%2Bnetworks&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></span> </li> <li id="cite_note-Windows_to_Linux-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-Windows_to_Linux_2-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAllen2004" class="citation book cs1">Allen, David (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=UD0h_GqgbHgC&q=network%2B+guide+to+networks"><i>Windows to Linux</i></a>. Prentice Hall. p. 192. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1423902459" title="Special:BookSources/1423902459"><bdi>1423902459</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Windows+to+Linux&rft.pages=192&rft.pub=Prentice+Hall&rft.date=2004&rft.isbn=1423902459&rft.aulast=Allen&rft.aufirst=David&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DUD0h_GqgbHgC%26q%3Dnetwork%252B%2Bguide%2Bto%2Bnetworks&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><span class="languageicon">(in Japanese)</span>, <a rel="nofollow" class="external text" href="http://journal.mycom.co.jp/special/2001/onlinenote/005.html">(Becky! tutorial)</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100131223322/http://journal.mycom.co.jp/special/2001/onlinenote/005.html">Archived</a> 2010-01-31 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, 2001-04-26.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20171021231958/http://www.pop4.org/pop4/pop4spec.html">"POP4 specification although pop is used to receive mail after system is not online"</a>. 2003. Archived from <a rel="nofollow" class="external text" href="http://www.pop4.org/pop4/pop4spec.html">the original</a> on 2017-10-21<span class="reference-accessdate">. Retrieved <span class="nowrap">2011-10-17</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=POP4+specification+although+pop+is+used+to+receive+mail+after+system+is+not+online.&rft.date=2003&rft_id=http%3A%2F%2Fwww.pop4.org%2Fpop4%2Fpop4spec.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://e.demon.net/helpdesk/producthelp/mail/sdps-tech.html/">Demon Online Help Centre</a> <a rel="nofollow" class="external text" href="https://archive.today/20110723084318/http://e.demon.net/helpdesk/producthelp/mail/sdps-tech.html/">Archived</a> 2011-07-23 at <a href="/wiki/Archive.today" title="Archive.today">archive.today</a>. E.demon.net (2013-01-23). Retrieved on 2013-07-17.</span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080913155355/http://mail.google.com/support/bin/answer.py?answer=34383">"Google Apps and Gmail differences"</a>. <i>Gmail Help Center</i>. Archived from <a rel="nofollow" class="external text" href="https://mail.google.com/support/bin/answer.py?answer=34383">the original</a> on September 13, 2008.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Gmail+Help+Center&rft.atitle=Google+Apps+and+Gmail+differences&rft_id=http%3A%2F%2Fmail.google.com%2Fsupport%2Fbin%2Fanswer.py%3Fanswer%3D34383&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">RFC 1939, page 19 (<a rel="nofollow" class="external free" href="https://datatracker.ietf.org/doc/rfc1939/">https://datatracker.ietf.org/doc/rfc1939/</a>)</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=13" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239549316">.mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}}</style><div class="refbegin" style=""> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHughes1998" class="citation book cs1">Hughes, L (1998). <i>Internet e-mail Protocols, Standards and Implementation</i>. Artech House Publishers. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-89006-939-5" title="Special:BookSources/0-89006-939-5"><bdi>0-89006-939-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Internet+e-mail+Protocols%2C+Standards+and+Implementation&rft.pub=Artech+House+Publishers&rft.date=1998&rft.isbn=0-89006-939-5&rft.aulast=Hughes&rft.aufirst=L&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJohnson2000" class="citation book cs1">Johnson, K (2000). <i>Internet Email Protocols: A Developer's Guide</i>. Addison-Wesley Professional. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-201-43288-9" title="Special:BookSources/0-201-43288-9"><bdi>0-201-43288-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Internet+Email+Protocols%3A+A+Developer%27s+Guide&rft.pub=Addison-Wesley+Professional&rft.date=2000&rft.isbn=0-201-43288-9&rft.aulast=Johnson&rft.aufirst=K&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLoshin1999" class="citation book cs1">Loshin, P (1999). <i>Essential Email Standards: RFCs and Protocols Made Practical</i>. John Wiley & Sons. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-471-34597-0" title="Special:BookSources/0-471-34597-0"><bdi>0-471-34597-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Essential+Email+Standards%3A+RFCs+and+Protocols+Made+Practical&rft.pub=John+Wiley+%26+Sons&rft.date=1999&rft.isbn=0-471-34597-0&rft.aulast=Loshin&rft.aufirst=P&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRhoton1999" class="citation book cs1">Rhoton, J (1999). <i>Programmer's Guide to Internet Mail: SMTP, POP, IMAP, and LDAP</i>. Elsevier. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-55558-212-5" title="Special:BookSources/1-55558-212-5"><bdi>1-55558-212-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Programmer%27s+Guide+to+Internet+Mail%3A+SMTP%2C+POP%2C+IMAP%2C+and+LDAP&rft.pub=Elsevier&rft.date=1999&rft.isbn=1-55558-212-5&rft.aulast=Rhoton&rft.aufirst=J&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWood1999" class="citation book cs1">Wood, D (1999). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/livesofcaptivere00petz"><i>Programming Internet Mail</i></a></span>. O'Reilly. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-56592-479-7" title="Special:BookSources/1-56592-479-7"><bdi>1-56592-479-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Programming+Internet+Mail&rft.pub=O%27Reilly&rft.date=1999&rft.isbn=1-56592-479-7&rft.aulast=Wood&rft.aufirst=D&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Flivesofcaptivere00petz&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://www.rfc-editor.org/std/std53.txt"><i>Post Office Protocol – Version 3</i></a>. IETF. May 1996.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Post+Office+Protocol+%E2%80%93+Version+3&rft.pub=IETF&rft.date=1996-05&rft_id=http%3A%2F%2Fwww.rfc-editor.org%2Fstd%2Fstd53.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3APost+Office+Protocol" class="Z3988"></span></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Post_Office_Protocol&action=edit&section=14" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://www.iana.org/assignments/port-numbers">IANA port number assignments</a></li> <li><a rel="nofollow" class="external text" href="http://www.eventhelix.com/RealtimeMantra/Networking/POP3.pdf">POP3 Sequence Diagram</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150503041335/http://www.eventhelix.com/RealtimeMantra/Networking/POP3.pdf">Archived</a> 2015-05-03 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (PDF)</li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output 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navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Email_clients" title="Template:Email clients"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Email_clients" title="Template talk:Email clients"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Email_clients" title="Special:EditPage/Template:Email clients"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Email_clients158" style="font-size:114%;margin:0 4em"><a href="/wiki/Email_client" title="Email client">Email clients</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Free software</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Current</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Alpine_(email_client)" title="Alpine (email client)">Alpine</a></li> <li><a href="/wiki/Balsa_(email_client)" title="Balsa (email client)">Balsa</a></li> <li><a href="/wiki/Citadel/UX" title="Citadel/UX">Citadel/UX</a></li> <li><a href="/wiki/Claws_Mail" title="Claws Mail">Claws Mail</a></li> <li><a href="/wiki/Cleancode_eMail" title="Cleancode eMail">Cleancode eMail</a></li> <li><a href="/wiki/GNOME_Evolution" title="GNOME Evolution">Evolution</a></li> <li><a href="/wiki/Fetchmail" title="Fetchmail">fetchmail</a></li> <li><a href="/wiki/Fdm_(software)" title="Fdm (software)">fdm</a></li> <li><a href="/wiki/Geary_(e-mail_client)" title="Geary (e-mail client)">Geary</a></li> <li><a href="/wiki/Getmail" title="Getmail">getmail</a></li> <li><a href="/wiki/GNUMail" title="GNUMail">GNUMail</a></li> <li><a href="/wiki/Gnus" title="Gnus">Gnus</a></li> <li><a href="/wiki/Gnuzilla" class="mw-redirect" title="Gnuzilla">Gnuzilla</a></li> <li><a href="/wiki/Internet_Messaging_Program" title="Internet Messaging Program">IMP</a></li> <li><a href="/wiki/K-9_Mail" title="K-9 Mail">K-9 Mail</a></li> <li><a href="/wiki/Kontact" title="Kontact">KMail</a></li> <li><a href="/wiki/Mahogany_(email_client)" title="Mahogany (email client)">Mahogany</a></li> <li><a href="/wiki/Mailpile" title="Mailpile">Mailpile</a></li> <li><a href="/wiki/Mailx" title="Mailx">Mailx</a></li> <li><a href="/wiki/Heirloom_Project" title="Heirloom Project">Mailx (Heirloom Project)</a></li> <li><a href="/wiki/Modest_(email_client)" title="Modest (email client)">Modest</a></li> <li><a href="/wiki/Mozilla_Thunderbird" title="Mozilla Thunderbird">Mozilla Thunderbird</a></li> <li><a href="/wiki/Mulberry_(email_client)" title="Mulberry (email client)">Mulberry</a></li> <li><a href="/wiki/Mutt_(email_client)" title="Mutt (email client)">Mutt</a></li> <li><a href="/wiki/MH_Message_Handling_System" title="MH Message Handling System">nmh / MH</a></li> <li><a href="/wiki/OfflineIMAP" title="OfflineIMAP">OfflineIMAP</a></li> <li><a href="/wiki/Roundcube" title="Roundcube">Roundcube</a></li> <li><a href="/wiki/SeaMonkey" title="SeaMonkey">SeaMonkey</a></li> <li><a href="/wiki/SquirrelMail" title="SquirrelMail">SquirrelMail</a></li> <li><a href="/wiki/Sylpheed" title="Sylpheed">Sylpheed</a></li> <li><a href="/wiki/Trojit%C3%A1" title="Trojitá">Trojitá</a></li> <li><a href="/wiki/YAM_(Yet_Another_Mailer)" class="mw-redirect" title="YAM (Yet Another Mailer)">YAM</a></li> <li><a href="/wiki/Zimbra" title="Zimbra">Zimbra</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Discontinued</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Arachne_(web_browser)" title="Arachne (web browser)">Arachne</a></li> <li><a href="/wiki/Beonex_Communicator" title="Beonex Communicator">Beonex Communicator</a></li> <li><a href="/wiki/BlitzMail" title="BlitzMail">BlitzMail</a></li> <li><a href="/wiki/Classilla" title="Classilla">Classilla</a></li> <li><a href="/wiki/Columbia_MM" title="Columbia MM">Columbia MM</a></li> <li><a href="/wiki/Elm_(email_client)" title="Elm (email client)">Elm</a></li> <li><a href="/wiki/Pale_Moon_(web_browser)#FossaMail" class="mw-redirect" title="Pale Moon (web browser)">FossaMail</a></li> <li><a href="/wiki/Hula_(software)" title="Hula (software)">Hula</a></li> <li><a href="/wiki/Mailody" title="Mailody">Mailody</a></li> <li><a href="/wiki/Mozilla_Mail_%26_Newsgroups" title="Mozilla Mail & Newsgroups">Mozilla Mail & Newsgroups</a></li> <li><a href="/wiki/Nylas_N1" class="mw-redirect" title="Nylas N1">Nylas N1</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Proprietary</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Freeware/Freemium</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/EM_Client" title="EM Client">eM Client</a></li> <li><a href="/wiki/EmailTray" title="EmailTray">EmailTray</a></li> <li><a href="/wiki/Foxmail" title="Foxmail">Foxmail</a></li> <li><a href="/wiki/Scribe_Mail" title="Scribe Mail">i.Scribe</a></li> <li><a href="/wiki/Mailbird" title="Mailbird">Mailbird</a></li> <li><a href="/wiki/Spark_(application)" class="mw-redirect" title="Spark (application)">Spark</a></li> <li><a href="/wiki/Spike_(application)" title="Spike (application)">Spike</a></li> <li><a href="/wiki/TouchMail" title="TouchMail">TouchMail</a></li> <li><a href="/wiki/Vivaldi_(web_browser)" title="Vivaldi (web browser)">Vivaldi Mail</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Retail</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hiri_(email_client)" title="Hiri (email client)">Hiri</a></li> <li><a href="/wiki/Bloomba" title="Bloomba">Bloomba/WordPerfect Mail</a></li> <li><a href="/wiki/Newton_(app)" class="mw-redirect" title="Newton (app)">Newton</a></li> <li><a href="/wiki/HCL_Domino" class="mw-redirect" title="HCL Domino">HCL Domino</a></li> <li><a href="/wiki/Scribe_Mail" title="Scribe Mail">InScribe</a></li> <li><a href="/wiki/Apple_Mail" title="Apple Mail">Apple Mail</a></li> <li><a href="/wiki/Mail_(Windows)" title="Mail (Windows)">Mail (Windows)</a></li> <li><a href="/wiki/Microsoft_Outlook" title="Microsoft Outlook">Microsoft Outlook</a></li> <li><a href="/wiki/Outlook_for_Windows" title="Outlook for Windows">Outlook for Windows</a></li> <li><a href="/wiki/GroupWise" title="GroupWise">Novell GroupWise</a></li> <li><a href="/wiki/Airmail_(email_client)" title="Airmail (email client)">Airmail</a></li> <li><a href="/wiki/Postbox_(email_client)" title="Postbox (email client)">Postbox</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Shareware</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Becky!" title="Becky!">Becky!</a></li> <li><a href="/wiki/Fort%C3%A9_Agent" title="Forté Agent">Forté Agent</a></li> <li><a href="/wiki/GyazMail" title="GyazMail">GyazMail</a></li> <li><a href="/wiki/The_Bat!" title="The Bat!">The Bat!</a></li> <li><a href="/wiki/Samsung_Email" class="mw-redirect" title="Samsung Email">Samsung Email</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Donationware</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pegasus_Mail" title="Pegasus Mail">Pegasus Mail</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Discontinued</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cc:Mail" title="Cc:Mail">cc:Mail</a></li> <li><a href="/wiki/Claris_Emailer" title="Claris Emailer">Claris Emailer</a></li> <li><a href="/wiki/Courier_(email_client)" title="Courier (email client)">Courier</a></li> <li><a href="/wiki/Cyberdog" title="Cyberdog">Cyberdog</a></li> <li><a href="/wiki/Cyberjack" title="Cyberjack">Cyberjack</a></li> <li><a href="/wiki/Embrowser" class="mw-redirect" title="Embrowser">Embrowser</a></li> <li><a href="/wiki/Eudora_(email_client)" title="Eudora (email client)">Eudora</a></li> <li><a href="/wiki/Mailbox_(application)" title="Mailbox (application)">Mailbox</a></li> <li><a href="/wiki/Microsoft_Entourage" title="Microsoft Entourage">Microsoft Entourage</a></li> <li><a href="/wiki/Microsoft_Internet_Mail_and_News" class="mw-redirect" title="Microsoft Internet Mail and News">Microsoft Internet Mail and News</a></li> <li><a href="/wiki/Microsoft_Mail" title="Microsoft Mail">Microsoft Mail</a></li> <li><a href="/wiki/Minnesota_Internet_Users_Essential_Tool" title="Minnesota Internet Users Essential Tool">MINUET</a></li> <li><a href="/wiki/Netscape_Mail_%26_Newsgroups" title="Netscape Mail & Newsgroups">Netscape Mail</a></li> <li><a href="/wiki/Netscape_Messenger_9" class="mw-redirect" title="Netscape Messenger 9">Netscape Messenger 9</a></li> <li><a href="/wiki/NeXTMail" class="mw-redirect" title="NeXTMail">NeXTMail</a></li> <li><a href="/wiki/Opera_Mail" title="Opera Mail">Opera Mail</a></li> <li><a href="/wiki/Outlook_Express" title="Outlook Express">Outlook Express</a></li> <li><a href="/wiki/Pine_(email_client)" title="Pine (email client)">Pine</a></li> <li><a href="/wiki/Pocomail" title="Pocomail">Pocomail</a></li> <li><a href="/wiki/POPmail" class="mw-redirect" title="POPmail">POPmail</a></li> <li><a href="/wiki/Sparrow_(email_client)" title="Sparrow (email client)">Sparrow</a></li> <li><a href="/wiki/Turnpike_(software)" title="Turnpike (software)">Turnpike</a></li> <li><a href="/wiki/WebSpyder" class="mw-redirect" title="WebSpyder">WebSpyder</a></li> <li><a href="/wiki/Windows_Live_Mail" title="Windows Live Mail">Windows Live Mail</a></li> <li><a href="/wiki/Windows_Messaging" title="Windows Messaging">Windows Messaging</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related technologies</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Simple_Mail_Transfer_Protocol" title="Simple Mail Transfer Protocol">SMTP</a></li> <li><a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">IMAP</a></li> <li><a href="/wiki/JSON_Meta_Application_Protocol" title="JSON Meta Application Protocol">JMAP</a></li> <li><a href="/wiki/Local_Mail_Transfer_Protocol" title="Local Mail Transfer Protocol">LMTP</a></li> <li><a class="mw-selflink selflink">POP</a></li> <li><a href="/wiki/Push-IMAP" title="Push-IMAP">Push-IMAP</a></li> <li><a href="/wiki/Simple_Mail_Access_Protocol" title="Simple Mail Access Protocol">SMAP</a></li> <li><a href="/wiki/UUCP" title="UUCP">UUCP</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Email" title="Email">Email</a></li> <li><a href="/wiki/Unicode_and_email" title="Unicode and email">Unicode and email</a></li></ul> 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