{"id":12064,"date":"2024-07-29T16:06:54","date_gmt":"2024-07-29T14:06:54","guid":{"rendered":"https:\/\/www.efidem.com\/?p=12064"},"modified":"2026-01-23T12:55:20","modified_gmt":"2026-01-23T11:55:20","slug":"smtp-email-common-errors-codes-meanings","status":"publish","type":"post","link":"https:\/\/www.efidem.com\/en\/blog\/2024\/07\/29\/smtp-email-erreurs-communes-codes-significations\/","title":{"rendered":"SMTP: Analysis of common errors, error codes and meanings"},"content":{"rendered":"<div data-elementor-type=\"wp-post\" data-elementor-id=\"12064\" class=\"elementor elementor-12064\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-1ab3d7c e-flex e-con-boxed e-con e-parent\" data-id=\"1ab3d7c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-f87172d elementor-widget elementor-widget-image\" data-id=\"f87172d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"180\" height=\"180\" src=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2020\/09\/efidem_new_logo.png\" class=\"attachment-large size-large wp-image-2439\" alt=\"deliverability\" srcset=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2020\/09\/efidem_new_logo.png 180w, https:\/\/www.efidem.com\/wp-content\/uploads\/2020\/09\/efidem_new_logo-150x150.png 150w\" sizes=\"(max-width: 180px) 100vw, 180px\" title=\"\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b7dd8d7 elementor-widget elementor-widget-heading\" data-id=\"b7dd8d7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">SMTP introduction<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-60ccfff elementor-widget elementor-widget-text-editor\" data-id=\"60ccfff\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>When you send an e-mail, you may encounter errors that prevent the message from being delivered. These errors are often indicated by error codes\u00a0<a href=\"https:\/\/www.efidem.com\/en\/powerful-french-emailing-software\/smtp-relay\/\" target=\"_blank\" rel=\"noopener\">SMTP<\/a> that provide information about the nature of the problem. Understanding the <a href=\"https:\/\/www.efidem.com\/en\/smtp-server-email-security-deliverability\/\">operation<\/a> of these error codes is essential for diagnosing and resolving messaging problems and\u00a0<a href=\"https:\/\/www.efidem.com\/en\/mail-delivrabilite-bonnes-pratiques-performantes\/\" target=\"_blank\" rel=\"noopener\">deliverability<\/a>. This article reviews the most common SMTP errors, their meanings and possible solutions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b2c1faa elementor-widget elementor-widget-heading\" data-id=\"b2c1faa\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">1 - Introduction to SMTP Error Codes<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4361e71 elementor-widget elementor-widget-text-editor\" data-id=\"4361e71\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>SMTP error codes are responses generated by the <a href=\"https:\/\/www.efidem.com\/en\/introduction-au-relais-smtp-quest-ce-que-cest-et-pourquoi-en-avez-vous-besoin\/\">SMTP servers<\/a> to indicate the status of a message. They appear on\u00a0<a href=\"https:\/\/www.efidem.com\/en\/easy-emailing-platform-snapshoot\/\" target=\"_blank\" rel=\"noopener\">Snapshoot<\/a>\u00a0in the form of three-digit numbers, where each digit has a specific meaning:<\/p><ul><li><p><strong>The first number<\/strong>\u00a0indicates the class of the response:<\/p><ul><li><code>2xx<\/code> : Successful (order accepted)<\/li><li><code>4xx<\/code> : Temporary error (try again later)<\/li><li><code>5xx<\/code> Permanent error (command failed)<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>The second number<\/strong> indicates the error category:<\/p><ul><li><code>x0x<\/code> : Syntax error<\/li><li><code>x1x<\/code> Status information<\/li><li><code>x2x<\/code> : Connections<\/li><li><code>x3x<\/code> E-mail address<\/li><li><code>x4x<\/code> : Message service<\/li><li><code>x5x<\/code> Mailbox status<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>The third number<\/strong> further specifies the SMTP error.<\/p><\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f4d3e86 elementor-widget elementor-widget-heading\" data-id=\"f4d3e86\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">2 - Common SMTP errors and what they mean<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8dcd97a elementor-widget elementor-widget-text-editor\" data-id=\"8dcd97a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>4xx errors: temporary errors, soft bounce<\/h2><p>These errors signal a temporary problem and indicate that the sender should try again later. The SMTP protocol is very precise and presents a status for each email sent.\u00a0<\/p><ul><li><h3><strong>421 Service Not Available<\/strong><\/h3><ul><li><strong>Meaning:<\/strong> Service is unavailable, often due to overload or maintenance.<\/li><li><strong>Solution:<\/strong> Wait a moment and try again. If the problem persists, contact the SMTP server administrator.<\/li><\/ul><\/li><li><h3><strong>450 Requested Mail Action Not Taken: Mailbox Unavailable<\/strong><\/h3><ul><li><strong>Meaning:<\/strong> Inbox temporarily unavailable, probably full.<\/li><li><strong>Solution:<\/strong> Try again after a while. If the problem persists, ask the recipient to check their inbox space.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>451 Requested Action Aborted: Local Error in Processing<\/strong><\/p><ul><li><strong>Meaning:<\/strong> A local error prevented the message from being processed.<\/li><li><strong>Solution:<\/strong> Wait a moment and try again. Also check your server for technical problems.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>452 Requested Action Not Taken: Insufficient System Storage<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The server has storage problems, often due to a full inbox.<\/li><li><strong>Solution:<\/strong> Try again later. If the problem persists, contact the server administrator.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><h2>5xx errors: permanent errors, hard bounce<\/h2><p>These errors indicate a definitive failure and usually require intervention to correct the problem.<\/p><ul><li><p><strong>500 Syntax Error, Command Unrecognised<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The command sent to the SMTP server contains a syntax error.<\/li><li><strong>Solution:<\/strong> Check the command sent. There could be a typo or incorrect configuration.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>501 Syntax Error in Parameters or Arguments<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The command parameters or arguments are incorrect.<\/li><li><strong>Solution:<\/strong> Check the arguments given in the SMTP command.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>502 Command Not Implemented<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The command is not supported by the SMTP server.<\/li><li><strong>Solution:<\/strong> Make sure you're using server-compatible commands.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>503 Bad Sequence of Commands<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The orders were sent in the wrong order.<\/li><li><strong>Solution:<\/strong> Check and correct the order of SMTP port commands.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>504 Command Parameter Not Implemented<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The command parameter is not supported by the server.<\/li><li><strong>Solution:<\/strong> Recheck port control settings.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>550 Requested Action Not Taken: Mailbox Unavailable<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The recipient's inbox is unavailable, often because the email address is incorrect.<\/li><li><strong>Solution:<\/strong> Check the recipient's email address and try again.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>551 User Not Local; Please Try Forwarding<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The recipient is unknown on this server, but could be found elsewhere.<\/li><li><strong>Solution:<\/strong> Check the email address and, if necessary, contact the recipient for a valid address.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>552 Requested Mail Action Aborted: Exceeded Storage Allocation<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The recipient's inbox has exceeded its storage capacity.<\/li><li><strong>Solution:<\/strong> Ask the recipient to free up space or use another address.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>553 Requested Action Not Taken: Mailbox Name Not Allowed<\/strong><\/p><ul><li><strong>Meaning:<\/strong> The recipient's email address is syntactically incorrect.<\/li><li><strong>Solution:<\/strong> Correct the email address and try again.<\/li><\/ul><\/li><\/ul><div>\u00a0<\/div><ul><li><p><strong>554 Transaction Failed\u00a0<\/strong><\/p><ul><li><strong>Meaning:<\/strong> A general error caused the transaction to fail.<\/li><li><strong>Solution:<\/strong> Recheck all email parameters and try again. If the problem persists, contact the server administrator.<\/li><\/ul><\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-b692cbf e-flex e-con-boxed e-con e-parent\" data-id=\"b692cbf\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-dd1b4d1 elementor-widget elementor-widget-heading\" data-id=\"dd1b4d1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Find out more <\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-beccaf9 elementor-widget elementor-widget-text-editor\" data-id=\"beccaf9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>You can test the SMTP service by opening a free test account with 2000 free e-mails per month at\u00a0<a href=\"https:\/\/snapshoot.efidem.com\/account\/newone\" rel=\"nofollow noopener\" target=\"_blank\">Snapshoot here<\/a>.<\/p><p>Or take a look at the\u00a0<a href=\"https:\/\/www.efidem.com\/en\/documentation\/\" target=\"_blank\" rel=\"noopener\">documentation\u00a0<\/a>techniques of our\u00a0<a href=\"https:\/\/www.efidem.com\/en\/efidem-software-saas\/\" target=\"_blank\" rel=\"noopener\">company<\/a>\u00a0and find out more about\u00a0<a href=\"https:\/\/www.efidem.com\/en\/blog-tips-emailing-sms\/\" target=\"_blank\" rel=\"noopener\">blog.<\/a><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-cd7e5ef elementor-widget elementor-widget-heading\" data-id=\"cd7e5ef\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Thanks for reading!<\/h4>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-9a88acf elementor-widget elementor-widget-image\" data-id=\"9a88acf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"450\" src=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__-1024x576.png\" class=\"attachment-large size-large wp-image-10734\" alt=\"SMTP\" srcset=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__-1024x576.png 1024w, https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__-300x169.png 300w, https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__-768x432.png 768w, https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__-1536x864.png 1536w, https:\/\/www.efidem.com\/wp-content\/uploads\/2022\/01\/API-SMTP-EMAIL-SMS__.png 1920w\" sizes=\"(max-width: 800px) 100vw, 800px\" title=\"\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6bfc88b elementor-widget elementor-widget-image\" data-id=\"6bfc88b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2025\/09\/bb54b258-d920-4dfa-86f0-0003ff6c6e96-1024x683.webp\" class=\"attachment-large size-large wp-image-16154\" alt=\"api email smtp\" srcset=\"https:\/\/www.efidem.com\/wp-content\/uploads\/2025\/09\/bb54b258-d920-4dfa-86f0-0003ff6c6e96-1024x683.webp 1024w, https:\/\/www.efidem.com\/wp-content\/uploads\/2025\/09\/bb54b258-d920-4dfa-86f0-0003ff6c6e96-300x200.webp 300w, https:\/\/www.efidem.com\/wp-content\/uploads\/2025\/09\/bb54b258-d920-4dfa-86f0-0003ff6c6e96-768x512.webp 768w, https:\/\/www.efidem.com\/wp-content\/uploads\/2025\/09\/bb54b258-d920-4dfa-86f0-0003ff6c6e96.webp 1536w\" sizes=\"(max-width: 800px) 100vw, 800px\" title=\"\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"<p>Introduction SMTP Lorsque vous envoyez un email, il est possible de rencontrer des erreurs qui emp\u00eachent la livraison du message. Ces erreurs sont souvent signal\u00e9es par des codes d&rsquo;erreur\u00a0SMTP sp\u00e9cifiques qui fournissent des informations sur la nature du probl\u00e8me. Comprendre le fonctionnement de ces codes d&rsquo;erreur est essentiel pour diagnostiquer et r\u00e9soudre les probl\u00e8mes de [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_lmt_disableupdate":"","_lmt_disable":"","footnotes":""},"categories":[46,85],"tags":[],"class_list":["post-12064","post","type-post","status-publish","format-standard","hentry","category-email-marketing","category-relais-smtp"],"acf":[],"modified_by":"@Efidem_csm","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/posts\/12064","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/comments?post=12064"}],"version-history":[{"count":58,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/posts\/12064\/revisions"}],"predecessor-version":[{"id":18529,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/posts\/12064\/revisions\/18529"}],"wp:attachment":[{"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/media?parent=12064"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/categories?post=12064"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.efidem.com\/en\/wp-json\/wp\/v2\/tags?post=12064"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}