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href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Bounce+message" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Bounce+message" title="You're encouraged to log in; however, it's not mandatory. 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data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Classification" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Classification"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Classification</span> </div> </a> <button aria-controls="toc-Classification-sublist" 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 Classification subsection</span> </button> <ul id="toc-Classification-sublist" class="vector-toc-list"> <li id="toc-Hard_bounces" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hard_bounces"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Hard bounces</span> </div> </a> <ul id="toc-Hard_bounces-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Soft_bounces" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Soft_bounces"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Soft bounces</span> </div> </a> <ul id="toc-Soft_bounces-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Delivery_errors" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Delivery_errors"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Delivery errors</span> </div> </a> <button aria-controls="toc-Delivery_errors-sublist" 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 Delivery errors subsection</span> </button> <ul id="toc-Delivery_errors-sublist" class="vector-toc-list"> <li id="toc-Bounce_due_to_lack_of_disk_space" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Bounce_due_to_lack_of_disk_space"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Bounce due to lack of disk space</span> </div> </a> <ul id="toc-Bounce_due_to_lack_of_disk_space-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bounce_due_to_unreachable_destination" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Bounce_due_to_unreachable_destination"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Bounce due to unreachable destination</span> </div> </a> <ul id="toc-Bounce_due_to_unreachable_destination-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bounce_from_forged_message" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Bounce_from_forged_message"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Bounce from forged message</span> </div> </a> <ul id="toc-Bounce_from_forged_message-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Other_causes" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Other_causes"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Other causes</span> </div> </a> <ul id="toc-Other_causes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Terminology" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Terminology"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Terminology</span> </div> </a> <ul id="toc-Terminology-sublist" class="vector-toc-list"> <li id="toc-Bouncing_vs._rejecting" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Bouncing_vs._rejecting"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5.1</span> <span>Bouncing vs. rejecting</span> </div> </a> <ul id="toc-Bouncing_vs._rejecting-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Silently_dropping_messages" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Silently_dropping_messages"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5.2</span> <span>Silently dropping messages</span> </div> </a> <ul id="toc-Silently_dropping_messages-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Causes_of_a_bounce_message" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Causes_of_a_bounce_message"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Causes of a bounce message</span> </div> </a> <ul id="toc-Causes_of_a_bounce_message-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Format" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Format"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Format</span> </div> </a> <ul id="toc-Format-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">5</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Related_RFCs" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Related_RFCs"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Related RFCs</span> </div> </a> <ul id="toc-Related_RFCs-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">7</span> <span>References</span> </div> </a> <ul id="toc-References-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">8</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" 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mw-first-heading"><span class="mw-page-title-main">Bounce message</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 9 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-9" 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">9 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Missatge_retornat" title="Missatge retornat – Catalan" lang="ca" hreflang="ca" data-title="Missatge retornat" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Bounce_Message" title="Bounce Message – German" lang="de" hreflang="de" data-title="Bounce Message" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%BE%DB%8C%D8%A7%D9%85_%D9%88%D8%A7%DA%AF%D8%B4%D8%AA" title="پیام واگشت – Persian" lang="fa" hreflang="fa" data-title="پیام واگشت" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr badge-Q70893996 mw-list-item" title=""><a href="https://fr.wikipedia.org/wiki/Delivery_Status_Notification" title="Delivery Status Notification – French" lang="fr" hreflang="fr" data-title="Delivery Status Notification" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Delivery_Status_Notification" title="Delivery Status Notification – Italian" lang="it" hreflang="it" data-title="Delivery Status Notification" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Bouncebericht" title="Bouncebericht – Dutch" lang="nl" hreflang="nl" data-title="Bouncebericht" 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/%E3%83%90%E3%82%A6%E3%83%B3%E3%82%B9%E3%83%A1%E3%83%BC%E3%83%AB" title="バウンスメール – Japanese" lang="ja" hreflang="ja" data-title="バウンスメール" 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-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%92%D0%BE%D0%B7%D0%B2%D1%80%D0%B0%D1%89%D1%91%D0%BD%D0%BD%D0%BE%D0%B5_%D0%BF%D0%B8%D1%81%D1%8C%D0%BC%D0%BE" title="Возвращённое письмо – Russian" lang="ru" hreflang="ru" data-title="Возвращённое письмо" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9F%D0%BE%D0%B2%D0%B5%D1%80%D0%BD%D1%83%D1%82%D0%B8%D0%B9_%D0%B5%D0%BB%D0%B5%D0%BA%D1%82%D1%80%D0%BE%D0%BD%D0%BD%D0%B8%D0%B9_%D0%BB%D0%B8%D1%81%D1%82" title="Повернутий електронний лист – Ukrainian" lang="uk" hreflang="uk" data-title="Повернутий електронний лист" data-language-autonym="Українська" data-language-local-name="Ukrainian" 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class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Automated message from an email system</div> <p>A <b>bounce message</b> or just "bounce" is an automated message from an email system, informing the sender of a previous message that the message has not been delivered (or some other delivery problem occurred). The original message is said to have "bounced". </p><p>This feedback may be immediate (some of the causes described here) or, if the sending system can retry, may arrive days later after these retries end. </p><p>More formal terms for bounce message include "Non-Delivery Report" or "Non-Delivery Receipt" (NDR), [Failed] "Delivery Status Notification" (DSN) message, or a "Non-Delivery Notification" (NDN).<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Classification">Classification</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=1" title="Edit section: Classification"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Although the <a href="/wiki/Simple_Mail_Transfer_Protocol" title="Simple Mail Transfer Protocol">SMTP</a> is a mature technology, counting more than thirty years, its architecture is increasingly strained by both normal and unsolicited load.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The email systems have been enhanced with reputation systems tied to the actual sender of the email, with the idea of recipient's email servers rejecting the email when a forged sender is used in the protocol.<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> </p><p>Therefore, two types of email bounces have been created: <i>hard bounces</i> and <i>soft bounces</i>.<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> Both of them affect the IP reputation of the sender because the <a href="/wiki/Email_service_provider_(marketing)" title="Email service provider (marketing)">Email Service Providers</a> (ESPs) consider the total bounce rate as a decision factor when directing the email into a user's Inbox. Briefly, the total bounce rate is calculated as the sum of the hard bounce rate and soft bounce rate. </p> <div class="mw-heading mw-heading3"><h3 id="Hard_bounces">Hard bounces</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=2" title="Edit section: Hard bounces"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hard bounces are permanent and they score higher in terms of sender's IP damage. Hard bounces occur when the sender's mail server determines that there is a high likelihood that the recipient is unavailable and is likely to remain so. A few of the occasions when hard bounces occur are when the recipients of the email find themselves in one of the following situations: incorrect identifier/incorrect domain (such as a typo in the email address or in the domain) or their server does not accept emails anymore. In this case, removal of the email addresses that bounce back is mandatory. </p> <div class="mw-heading mw-heading3"><h3 id="Soft_bounces">Soft bounces</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=3" title="Edit section: Soft bounces"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Soft bounces are temporary. A bounced message that experiences a soft bounce may be tried to be redelivered at another time.<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> Soft bounces happen when the recipient of the email has either a full Inbox and therefore no space to store another email is available, or a limit on the size of the emails that it is allowed to receive has been reached. Additional situations in which a soft bounce appears is a block set up on the recipient's email to mark a certain sender as a 'spam' sender, or to blacklist a certain sender. Moreover, a temporary suspension of the recipient's email or a temporary error on the server are also causes of a soft bounce. </p> <div class="mw-heading mw-heading2"><h2 id="Delivery_errors">Delivery errors</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=4" title="Edit section: Delivery errors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Errors may occur at multiple places in mail delivery. A sender may sometimes receive a bounce message from their <i>own</i> mail server, reporting that it has been unable to send a message, or alternatively from a <i>recipient's</i> mail server reporting that although it had accepted the message, it is unable to deliver it to the specified user. When a server accepts a message for delivery, it is also accepting the responsibility to deliver a bounce message in the event that delivery fails. </p> <div class="mw-heading mw-heading3"><h3 id="Bounce_due_to_lack_of_disk_space">Bounce due to lack of disk space</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=5" title="Edit section: Bounce due to lack of disk space"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When an e-mail arrives at the destination server for an address (such as mymail.example, when sending to <i>alice@mymail.example</i>), it may be that the mail <a href="/wiki/Daemon_(computing)" title="Daemon (computing)">daemon</a> is unable to deposit the message in the specified user's mailbox if the underlying <a href="/wiki/Hard_disk_drive" title="Hard disk drive">hard drive</a> of the server has insufficient space. </p> <div class="mw-heading mw-heading3"><h3 id="Bounce_due_to_unreachable_destination">Bounce due to unreachable destination</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=6" title="Edit section: Bounce due to unreachable destination"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When sending an e-mail, the service from which the e-mail is sent may be unable to reach the destination address. In such case, the sender would receive a bounce message from their own mail server. Common causes for mail servers being unable to reach a destination: </p> <ul><li>Unable to <a href="/wiki/DNS_resolver" class="mw-redirect" title="DNS resolver">resolve</a> the destination address. For example, if the domain name does not exist.</li> <li>Unable to establish a <a href="/wiki/Internet_Protocol" title="Internet Protocol">connection</a> with the destination address. For example, if the IP address is not assigned to a server, or if the server is <a href="/wiki/Online_and_offline" title="Online and offline">offline</a>.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Bounce_from_forged_message">Bounce from forged message</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=7" title="Edit section: Bounce from forged message"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Users may receive erroneous bounce messages about messages they never actually sent. This can happen in particular in the context of <a href="/wiki/Email_spam" title="Email spam">email spam</a> or <a href="/wiki/Computer_virus" title="Computer virus">email viruses</a>, where a spammer (sender) may forge a message to another user (intended recipient of spam), and forges the message to appear from yet another user (a third party). If the message cannot be delivered to the intended recipient, then the bounce message would be "returned" to the third party instead of the spammer. This is called <a href="/wiki/Backscatter_(email)" title="Backscatter (email)">backscatter</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Other_causes">Other causes</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=8" title="Edit section: Other causes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Had the <i>library.example</i> mail server known that the message would be undeliverable (for instance, if Jill had no user account there) then it would <i>not</i> have accepted the message in the first place, and therefore would not have sent the bounce. Instead, it would have rejected the message with an SMTP error code. This would leave <i>Jack's</i> mail server (at <i>store.example</i>) the obligation to create and deliver a bounce. </p> <div class="mw-heading mw-heading3"><h3 id="Terminology">Terminology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=9" title="Edit section: Terminology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>Bounces</b> are a special form of <a href="/wiki/Autoresponder" title="Autoresponder">autoresponder</a>. Auto-responses (automatic replies) are mails sent by a program—as opposed to a human user—in reply to a received mail and sent to the <a href="/wiki/Bounce_address" title="Bounce address">bounce address</a>. </p><p>Examples of other auto replies are <b>vacation</b> mails, <b>challenges</b> from <a href="/wiki/Challenge-response_spam_filtering" class="mw-redirect" title="Challenge-response spam filtering">challenge-response spam filtering</a>, replies from <a href="/wiki/Mailing_list" title="Mailing list">list servers</a>, and <a href="/wiki/Feedback_Loop_(email)" class="mw-redirect" title="Feedback Loop (email)">feedback reports</a>. These other auto replies are discussed in RFC 3834: auto replies should be sent to the <code>Return-Path</code> stated in the received mail which has triggered the auto reply, and this response is typically sent with an empty Return-Path; otherwise auto responders could be trapped in sending auto replies back and forth.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (June 2010)">citation needed</span></a></i>]</sup> </p><p>The <code>Return-Path</code> is visible in delivered mail as header field <code>Return-Path</code> inserted by the SMTP <a href="/wiki/Mail_delivery_agent" class="mw-redirect" title="Mail delivery agent">mail delivery agent</a> (<b>MDA</b>) (which is usually combined with a <b><a href="/wiki/Mail_transfer_agent" class="mw-redirect" title="Mail transfer agent">mail transfer agent</a></b>, or <b>MTA</b>). The MDA simply copies the <a href="/wiki/Reverse_path" class="mw-redirect" title="Reverse path">reverse path</a> in the SMTP <code>MAIL FROM</code> command into the <code>Return-Path</code>. The MDA also removes bogus <code>Return-Path</code> header fields inserted by other MTAs; this header field is generally guaranteed to reflect the last reverse path seen in the <code>MAIL FROM</code> command. </p><p>Today these paths are normally reduced to ordinary <a href="/wiki/Email_address" title="Email address">email addresses</a>, as the old SMTP '<a href="/wiki/Source_routing" title="Source routing">source routing</a>' was deprecated in 1989; for some historical background info see <a href="/wiki/Sender_Rewriting_Scheme" title="Sender Rewriting Scheme">Sender Rewriting Scheme</a>. One special form of a path still exists: the empty path <code>MAIL FROM:<></code>, used for many auto replies and especially all bounces. </p><p>In a strict sense, bounces sent with a non-empty <code>Return-Path</code> are incorrect. RFC 3834 offers some <a href="/wiki/Heuristic_(computer_science)" title="Heuristic (computer science)">heuristics</a> to identify incorrect bounces based on the local part (left hand side before the "@") of the address in a non-empty <code>Return-Path</code>, and it even defines a mail header field, <code>Auto-Submitted</code>, to identify auto replies. But the mail header is a part of the mail data (SMTP command <code>DATA</code>), and MTAs typically don't look <i>into</i> the mail. They deal with the <i>envelope</i>, that includes the <code>MAIL FROM</code> address (a.k.a. <code>Return-Path</code>, <code>Envelope-FROM</code>, or "reverse path") but not, e.g., the RFC 2822-<code>From</code> in the mail header field <code>From</code>. These details are important for schemes like <a href="/wiki/Bounce_Address_Tag_Validation" title="Bounce Address Tag Validation">BATV</a>. </p><p>The remaining bounces with an empty <code>Return-Path</code> are <b>non-delivery reports</b> (<b>NDRs</b>) or <b>delivery status notifications</b> (DSNs). DSNs can be explicitly solicited with an SMTP Service Extension, however it is not widely used. Explicit requests for delivery failure details is much more commonly implemented with <a href="/wiki/Variable_envelope_return_path" title="Variable envelope return path">variable envelope return path</a> (VERP), while explicit requests for them are rarely implemented.<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><p>NDRs are a basic SMTP function. As soon as an MTA has accepted a mail for forwarding or delivery it cannot silently delete ("drop") it; it has to create and send a bounce message to the <i>originator</i> if forwarding or delivery failed. </p> <div class="mw-heading mw-heading4"><h4 id="Bouncing_vs._rejecting">Bouncing vs. rejecting</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=10" title="Edit section: Bouncing vs. rejecting"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Excluding MDAs, all MTAs forward mails to another MTA. This next MTA is free to <i>reject</i> the mail with an SMTP error message like <i>"user unknown"</i>, <i>"over quota"</i>, etc. At this point the sending MTA has to <i>bounce the message</i>, i.e. inform its originator. A bounce may arise also without a rejecting MTA, or as RFC 5321 puts it: </p> <blockquote><p><i>"If an SMTP server has accepted the task of relaying the mail and later finds that the destination is incorrect or that the mail cannot be delivered for some other reason, then it MUST construct an "undeliverable mail" notification message and send it to the originator of the undeliverable mail (as indicated by the reverse-path)."</i></p></blockquote> <p>This rule is essential for SMTP: as the name says, it's a 'simple' protocol, it cannot reliably work if mail silently vanishes in black holes, so bounces are required to spot and fix problems. </p> <div class="mw-heading mw-heading4"><h4 id="Silently_dropping_messages">Silently dropping messages</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=11" title="Edit section: Silently dropping messages"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Today, however, it can be common to receive mostly <a href="/wiki/Email_spam" title="Email spam">spam</a> emails, which usually uses forged <code>Return-Path</code>s. It is then often impossible for the MTA to inform the originator, and sending a bounce to the forged <code>Return-Path</code> would hit an innocent third party. In addition, there are specific reasons why it is preferable to silently <i>drop</i> a message rather than <i>reject</i> it (let alone <i>bounce</i> it): </p> <ul><li><a href="/wiki/Bayesian_spam_filter" class="mw-redirect" title="Bayesian spam filter">Heuristically filtered spam</a>. Spam filters are not perfect. Rejecting spam based on content filtering implies giving to spammers a test environment where they can try several alternatives until they find content that passes the filter.</li> <li><a href="/wiki/Computer_virus" title="Computer virus">Viruses</a> and <a href="/wiki/Computer_worm" title="Computer worm">worms</a>. Most times these are sent automatically from an infected machine. Since a bounce may contain a copy of the worm itself, it may contribute to its diffusion.</li></ul> <p>Quoting again RFC 5321, section 6.2: </p> <blockquote><p><i>"As discussed in Section 7.8 and Section 7.9 below, dropping mail without notification of the sender is permitted in practice. However, it is extremely dangerous and violates a long tradition and community expectations that mail is either delivered or returned. If silent message-dropping is misused, it could easily undermine confidence in the reliability of the Internet's mail systems. So silent dropping of messages should be considered only in those cases where there is very high confidence that the messages are seriously fraudulent or otherwise inappropriate."</i></p></blockquote> <p>Not validating the sender is an inherent flaw in today's SMTP, which is without the deprecated source routes mentioned earlier. This is addressed by various proposals, most directly by <a href="/wiki/Bounce_Address_Tag_Validation" title="Bounce Address Tag Validation">BATV</a> and <a href="/wiki/Sender_Policy_Framework" title="Sender Policy Framework">SPF</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Causes_of_a_bounce_message">Causes of a bounce message</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=12" title="Edit section: Causes of a bounce message"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are many reasons why an email may bounce. One reason is if the recipient address is misspelled, or simply does not exist on the receiving system. This is a <i>user unknown</i> condition. Other reasons include resource exhaustion — such as a full disk — or the rejection of the message due to <a href="/wiki/Email_spam" title="Email spam">spam</a> filters. In addition, there are <a href="/wiki/Mail_user_agent" class="mw-redirect" title="Mail user agent">MUAs</a> that allow users to "bounce" a message on demand.<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> These user-initiated bounces are bogus bounces; by definition, a real bounce is automated, and is emitted by a MTA or MDA. </p><p>Bounce messages in <a href="/wiki/SMTP" class="mw-redirect" title="SMTP">SMTP</a> are sent with the envelope sender address <code><></code>, known as the <i>null sender address</i>. They are frequently sent with a <code>From:</code> header address of <code>MAILER-DAEMON</code> at the recipient site. </p><p>Typically, a bounce message will contain several pieces of information to help the original sender in understanding the reason their message was not delivered: </p> <ul><li>The date and time the message was bounced,</li> <li>The identity of the mail server that bounced it,</li> <li>The reason that it was bounced (e.g. <i>user unknown</i> or <i>mailbox full</i>),</li> <li>The headers of the bounced message, and</li> <li>Some or all of the content of the bounced message.</li></ul> <p>RFC 3463 describes the codes used to indicate the bounce reason. Common codes are 5.1.1 (Unknown user), 5.2.2 (Mailbox full) and 5.7.1 (Rejected by security policy/mail filter). </p> <div class="mw-heading mw-heading2"><h2 id="Format">Format</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=13" title="Edit section: Format"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Bounce-DSN-MTA-names.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Bounce-DSN-MTA-names.png/350px-Bounce-DSN-MTA-names.png" decoding="async" width="350" height="194" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Bounce-DSN-MTA-names.png/525px-Bounce-DSN-MTA-names.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Bounce-DSN-MTA-names.png/700px-Bounce-DSN-MTA-names.png 2x" data-file-width="1052" data-file-height="584" /></a><figcaption>MTAs involved in a <i>reject</i> are named according to the point of view of the <i>Reporting MTA</i>. MTA names are often of type <i>dns</i>.</figcaption></figure><p> The format for the reporting of administrative messages is defined by <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><a href="/wiki/RFC_(identifier)" class="mw-redirect" title="RFC (identifier)">RFC</a> <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc6522">6522</a>. A DSN may be a <a href="/wiki/MIME" title="MIME">MIME</a> <i>multipart/report</i> message composed of three parts: </p><ol><li>a human readable explanation;</li> <li>a machine parsable <i>message/delivery-status</i>, a list of <i>"name: type; value"</i> lines that state several possible fields; and</li> <li>the original message, or a portion thereof, as an entity of type <i>message/rfc822</i>.</li></ol> <p>The second part of a DSN is also quite readable. It is essential to understand which MTA played which role. The <i>Reporting-MTA</i> is responsible for composing and sending the DSN. </p><p>When a <i>Remote-MTA</i> rejects a message during an SMTP transaction, a field <i>Diagnostic-Code</i> of type <i>smtp</i> may be used to report that value. Note that beside the numerical 3-digit value, the SMTP response contains itself a human readable part. The information </p> <div class="mw-highlight mw-highlight-lang-email mw-content-ltr" dir="ltr"><pre><span></span><span class="nt">Remote-MTA:</span><span class="w"> </span>dns;<span class="w"> </span><span class="nf">smtp.store.example</span><span class="w"> </span>[<span class="mi">192.0.2.3</span>] <span class="nt">Diagnostic-Code:</span><span class="w"> </span>smtp;<span class="w"> </span>550<span class="w"> </span>No<span class="w"> </span>such<span class="w"> </span>user<span class="w"> </span>here </pre></div> <dl><dd>is sometimes reported as, e.g.,</dd></dl> <pre>while talking to smtp.store.example [192.0.2.3] >>> RCPT TO:<nonexistinguser@store.example> <<< 550 No such user here </pre> <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=Bounce_message&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Backscatter_(email)" title="Backscatter (email)">Backscatter</a> (Backscatter of email spam)</li> <li><a href="/wiki/Bounce_Address_Tag_Validation" title="Bounce Address Tag Validation">Bounce Address Tag Validation</a> (BATV)</li> <li><a href="/wiki/Email_tracking" title="Email tracking">Email tracking</a></li> <li><a href="/wiki/Sender_Policy_Framework" title="Sender Policy Framework">Sender Policy Framework</a> (SPF)</li> <li><a href="/wiki/DomainKeys_Identified_Mail" title="DomainKeys Identified Mail">DomainKeys Identified Mail</a> (DKIM)</li> <li><a href="/wiki/Sender_Rewriting_Scheme" title="Sender Rewriting Scheme">Sender Rewriting Scheme</a> (SRS)</li> <li><a href="/wiki/Simple_Mail_Transfer_Protocol" title="Simple Mail Transfer Protocol">Simple Mail Transfer Protocol</a> (SMTP)</li> <li><a href="/wiki/Variable_envelope_return_path" title="Variable envelope return path">Variable envelope return path</a> (VERP)</li></ul> <div class="mw-heading mw-heading2"><h2 id="Related_RFCs">Related RFCs</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Bounce_message&action=edit&section=15" title="Edit section: Related RFCs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><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/rfc5321">5321</a> - Simple Mail Transfer 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/rfc3461">3461</a> - Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs)</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/rfc6522">6522</a> - The Multipart/Report Media Type for the Reporting of Mail System Administrative Messages</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/rfc3463">3463</a> - Enhanced Status Codes for SMTP</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/rfc3464">3464</a> - An Extensible Message Format for Delivery Status Notifications</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/rfc3834">3834</a> - Recommendations for Automatic Responses to Electronic Mail</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/rfc5337">5337</a> - Internationalized Delivery Status and Disposition Notifications</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=Bounce_message&action=edit&section=16" 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-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation cs2">"Examples of rogue unsolicited email messages", <i>Security Risks in Social Media Technologies</i>, Elsevier, pp. 241–242, 2013, <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fb978-1-84334-714-9.50022-x">10.1016/b978-1-84334-714-9.50022-x</a>, <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-84334-714-9" title="Special:BookSources/978-1-84334-714-9"><bdi>978-1-84334-714-9</bdi></a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Security+Risks+in+Social+Media+Technologies&rft.atitle=Examples+of+rogue+unsolicited+email+messages&rft.pages=241-242&rft.date=2013&rft_id=info%3Adoi%2F10.1016%2Fb978-1-84334-714-9.50022-x&rft.isbn=978-1-84334-714-9&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAferganMikeBeverlyRobert2005" class="citation journal cs1">AferganMike; BeverlyRobert (2005-01-01). "The state of the email address". <i>ACM SIGCOMM Computer Communication Review</i>. <b>35</b>: 29–36. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F1052812.1052822">10.1145/1052812.1052822</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:16604893">16604893</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=ACM+SIGCOMM+Computer+Communication+Review&rft.atitle=The+state+of+the+email+address&rft.volume=35&rft.pages=29-36&rft.date=2005-01-01&rft_id=info%3Adoi%2F10.1145%2F1052812.1052822&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A16604893%23id-name%3DS2CID&rft.au=AferganMike&rft.au=BeverlyRobert&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1">"Countering illegal traffic: A snapshot of monitoring and enforcement". 2016-09-27. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.18356%2F0f24bf9f-en">10.18356/0f24bf9f-en</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Countering+illegal+traffic%3A+A+snapshot+of+monitoring+and+enforcement&rft.date=2016-09-27&rft_id=info%3Adoi%2F10.18356%2F0f24bf9f-en&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" class="Z3988"></span> <span class="cs1-visible-error citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_journal" title="Template:Cite journal">cite journal</a>}}</code>: </span><span class="cs1-visible-error citation-comment">Cite journal requires <code class="cs1-code">|journal=</code> (<a href="/wiki/Help:CS1_errors#missing_periodical" title="Help:CS1 errors">help</a>)</span></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://kingsmtp.com/the-ultimate-guide-to-preventing-yahoo-email-bounces/">"Hard Bounces vs Soft Bounces and how to remove them | Blog"</a>. <i>kingsmtp.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2024-10-01</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=kingsmtp.com&rft.atitle=Hard+Bounces+vs+Soft+Bounces+and+how+to+remove+them+%7C+Blog&rft_id=https%3A%2F%2Fkingsmtp.com%2Fthe-ultimate-guide-to-preventing-yahoo-email-bounces%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" 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"><style data-mw-deduplicate="TemplateStyles:r1041539562">.mw-parser-output .citation{word-wrap:break-word}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}</style><span class="citation patent"><a rel="nofollow" class="external autonumber" href="https://patents.google.com/patent/US7917588B2/en">[1]</a>, "Managing delivery of electronic messages using bounce profiles", issued 2005-05-26</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Apatent&rft.number=&rft.cc=&rft.title=Managing+delivery+of+electronic+messages+using+bounce+profiles&rft.date=2005-05-26"><span style="display: none;"> </span></span></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 id="CITEREFStross2008" class="citation news cs1">Stross, Randall (2008-06-15). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2008/06/15/technology/15digi.html">"In the E-Mail Relay, Not Every Handoff Is Smooth"</a>. <i>The New York Times</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2010-04-26</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=In+the+E-Mail+Relay%2C+Not+Every+Handoff+Is+Smooth&rft.date=2008-06-15&rft.aulast=Stross&rft.aufirst=Randall&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2008%2F06%2F15%2Ftechnology%2F15digi.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRayRay,_John2005" class="citation news cs1">Ray, William; Ray, John (2005-07-15). <a rel="nofollow" class="external text" href="http://www.informit.com/articles/article.aspx?p=401141&seqNum=2">"Using Internet Applications in Mac OS X Tiger"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2008-10-02</span></span>. <q>Another method of defeating spam is to bounce mail back to them. This creates the appearance that your account doesn't exist and, if you're lucky, results in having your name removed from their lists.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Using+Internet+Applications+in+Mac+OS+X+Tiger&rft.date=2005-07-15&rft.aulast=Ray&rft.aufirst=William&rft.au=Ray%2C+John&rft_id=http%3A%2F%2Fwww.informit.com%2Farticles%2Farticle.aspx%3Fp%3D401141%26seqNum%3D2&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" class="Z3988"></span>, and <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBreen2006" class="citation news cs1">Breen, Christopher (2006-01-27). <a rel="nofollow" class="external text" href="http://www.macworld.com/article/49156/2006/01/creepbounce.html/weblogs/www.idgconnect.com">"Bouncing the creeps"</a>. Macworld<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-10-02</span></span>. <q>As you're probably aware, using Mail's Bounce command (Message > Bounce) isn't effective against spammers because nearly all the spam your receive carries a forged "from" address.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Bouncing+the+creeps&rft.date=2006-01-27&rft.aulast=Breen&rft.aufirst=Christopher&rft_id=http%3A%2F%2Fwww.macworld.com%2Farticle%2F49156%2F2006%2F01%2Fcreepbounce.html%2Fweblogs%2Fwww.idgconnect.com&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABounce+message" class="Z3988"></span></span> </li> </ol></div></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=Bounce_message&action=edit&section=17" 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="http://www.techzoom.net/Papers/Mail_Non_Delivery_Notice_Attacks_(2004).pdf">Mail DDoS Attacks through Non Delivery Messages</a></li> <li><a rel="nofollow" class="external text" href="https://docs.microsoft.com/en-us/exchange/mail-flow/non-delivery-reports-and-bounce-messages/non-delivery-reports-and-bounce-messages?view=exchserver-2019">Microsoft DSNs and NDRs in Exchange Server</a></li> <li><a rel="nofollow" class="external text" href="https://www.maxprog.com/site/support/us/emailbouncehandler/understanding_bounce_e-mails.php">Understanding Bounce Email</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Bounce_message&oldid=1248783477">https://en.wikipedia.org/w/index.php?title=Bounce_message&oldid=1248783477</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Email" title="Category:Email">Email</a></li><li><a href="/wiki/Category:Email_authentication" title="Category:Email authentication">Email authentication</a></li><li><a href="/wiki/Category:Internet_Standards" title="Category:Internet Standards">Internet Standards</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:CS1_errors:_missing_periodical" title="Category:CS1 errors: missing periodical">CS1 errors: missing periodical</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:All_articles_with_unsourced_statements" title="Category:All articles with unsourced statements">All articles with unsourced statements</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements_from_June_2010" title="Category:Articles with unsourced statements from June 2010">Articles with unsourced statements from June 2010</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 1 October 2024, at 13:10<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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