{"id":34539,"date":"2026-03-16T12:42:10","date_gmt":"2026-03-16T12:42:10","guid":{"rendered":"https:\/\/1grid.co.za\/knowledge\/?post_type=ht_kb&#038;p=34539"},"modified":"2026-03-16T12:42:13","modified_gmt":"2026-03-16T12:42:13","slug":"smtp-error-535-authentication-failed-how-to-fix","status":"publish","type":"ht_kb","link":"https:\/\/1grid.co.za\/knowledge\/smtp-error-535-authentication-failed-how-to-fix-it\/","title":{"rendered":"SMTP Error 535: Authentication Failed (How to Fix It)"},"content":{"rendered":"\n<p>If\u00a0you&#8217;re\u00a0seeing\u00a0<strong>SMTP Error 535: Authentication Failed<\/strong>, your email client cannot log into the outgoing mail server.\u00a0<\/p>\n\n\n\n<p><strong>This&nbsp;guide will help you:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-identify-the-exact-cause\">Identify\u00a0the exact cause\u00a0<\/li>\n\n\n\n<li id=\"htoc-correct-your-authentication-settings\">Correct your authentication settings\u00a0<\/li>\n\n\n\n<li id=\"htoc-secure-your-mailbox\">Secure your mailbox\u00a0<\/li>\n\n\n\n<li id=\"htoc-send-email-successfully-again\">Send email successfully again\u00a0<\/li>\n<\/ul>\n\n\n\n<p>Nothing in this process will affect your website, hosting, or existing mail data.&nbsp;<\/p>\n\n\n\n<p>By the end of this guide,&nbsp;you\u2019ll&nbsp;confidently resolve SMTP 535 errors without contacting support.&nbsp;<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1600\" height=\"600\" src=\"https:\/\/1grid.co.za\/knowledge\/wp-content\/uploads\/2026\/03\/1-grid-Images-for-KB-Articles-1000-x-600-px-8.png\" alt=\"SMTP Error 535: Authentication Failed (How to Fix It)\" class=\"wp-image-34543\"\/><\/figure>\n<\/div>\n\n\n<div class=\"wp-block-ht-block-toc  is-style-outline htoc htoc--position-wide toc-list-style-plain\" data-htoc-state=\"expanded\"><span class=\"htoc__title\"><span class=\"ht_toc_title\">Table of Contents<\/span><span class=\"htoc__toggle\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"16\" height=\"16\"><g fill=\"#444\"><path d=\"M15 7H1c-.6 0-1 .4-1 1s.4 1 1 1h14c.6 0 1-.4 1-1s-.4-1-1-1z\"><\/path><path d=\"M15 1H1c-.6 0-1 .4-1 1s.4 1 1 1h14c.6 0 1-.4 1-1s-.4-1-1-1zM15 13H1c-.6 0-1 .4-1 1s.4 1 1 1h14c.6 0 1-.4 1-1s-.4-1-1-1z\"><\/path><\/g><\/svg><\/span><\/span><div class=\"htoc__itemswrap\"><ul class=\"ht_toc_list\"><li class=\"\"><a href=\"#htoc-what-smtp-error-535-means\">What SMTP Error 535 Means&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-why-this-happens\">Why This Happens&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-who-this-applies-to\">Who This Applies To&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-step-by-step-fix-for-smtp-error-535-authentication-failed\">Step-by-Step Fix&nbsp;for SMTP Error 535&nbsp;\u2013 Authentication Failed&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-quick-fixes-for-common-smtp-535-variations\">Quick Fixes for Common SMTP 535 Variations&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-advanced-optional-fixes-for-technical-users\">Advanced (Optional) Fixes (For Technical Users)&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-before-you-move-on\">Before You Move&nbsp;On&nbsp;&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-if-this-didn-t-work\">If This&nbsp;Didn\u2019t&nbsp;Work&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-common-mistakes-to-avoid\">Common Mistakes to Avoid&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-empowering-insight\">Empowering Insight&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-next-recommended-steps\">Next Recommended Steps&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-faqs\">FAQs&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-additional-resources\">Additional&nbsp;Resources&nbsp;<\/a><\/li><\/ul><\/div><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-what-smtp-error-535-means\"><strong>What SMTP Error 535 Means<\/strong>&nbsp;<\/h2>\n\n\n\n<p><strong>SMTP 535<\/strong>&nbsp;means the mail server rejected the login credentials used to send email.&nbsp;<\/p>\n\n\n\n<p>In simple terms:&nbsp;<\/p>\n\n\n\n<p>Your email app tried to log in,\u00a0but the\u00a0server said:\u00a0<strong><em>\u201cThese credentials are incorrect or not allowed.\u201d<\/em><\/strong>\u00a0<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-why-this-happens\"><strong>Why This Happens<\/strong>&nbsp;<\/h2>\n\n\n\n<p>Common causes include:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-incorrect-password\">Incorrect password\u00a0<\/li>\n\n\n\n<li id=\"htoc-using-the-mailbox-name-instead-of-the-full-email-address\">Using the mailbox name instead of the full email address\u00a0<\/li>\n\n\n\n<li id=\"htoc-password-recently-changed-but-not-updated-on-all-devices\">Password recently changed, but not updated on all devices\u00a0<\/li>\n\n\n\n<li id=\"htoc-smtp-authentication-disabled\">SMTP authentication disabled\u00a0<\/li>\n\n\n\n<li id=\"htoc-ssl-tls-encryption-disabled\">SSL\/TLS encryption disabled\u00a0<\/li>\n\n\n\n<li id=\"htoc-account-temporarily-restricted-due-to-repeated-failures\">Account temporarily restricted due to repeated failures\u00a0<\/li>\n\n\n\n<li id=\"htoc-unsupported-authentication-method\">Unsupported authentication method\u00a0<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-who-this-applies-to\"><strong>Who This Applies To<\/strong>&nbsp;<\/h2>\n\n\n\n<p>This error may occur if you:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-use-outlook-apple-mail-thunderbird-gmail-app-or-mobile-mail-apps\">Use Outlook, Apple Mail, Thunderbird, Gmail app, or mobile mail apps\u00a0<\/li>\n\n\n\n<li id=\"htoc-recently-changed-your-email-password\">Recently changed your email password\u00a0<\/li>\n\n\n\n<li id=\"htoc-are-setting-up-a-new-device\">Are setting up a new device\u00a0<\/li>\n\n\n\n<li id=\"htoc-see-535-authentication-failed-in-bounce-messages\">See \u201c535 Authentication Failed\u201d in <a href=\"https:\/\/1grid.co.za\/knowledge\/why-emails-bounce-back-error-messages-and-how-to-fix-them\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>bounce messages<\/strong><\/a>\u00a0<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-step-by-step-fix-for-smtp-error-535-authentication-failed\"><strong>Step-by-Step Fix&nbsp;for SMTP Error 535&nbsp;\u2013 Authentication Failed<\/strong>&nbsp;<\/h2>\n\n\n\n<p>Follow these steps in order.&nbsp;<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>1: Confirm the Full Error Message\u00a0<\/strong><\/summary>\n<p id=\"htoc-1-confirm-the-full-error-message\">Open the bounce message or email app error details.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-ensure-it-specifically-references\">Ensure it specifically references:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-535-authentication-failed\" class=\"wp-block-code\"><code>535 Authentication failed&nbsp;\n535 Incorrect authentication data&nbsp;\n535 5.7.8 Username and Password not accepted&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-1-confirm-the-full-error-message1\">If it shows a different SMTP code, refer to our<strong>\u00a0<a href=\"https:\/\/1grid.co.za\/knowledge\/a-guide-to-smtperror-codes\/\" target=\"_blank\" rel=\"noreferrer noopener\">SMTP Error Codes<\/a><\/strong>\u00a0guide.\u00a0<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>2: Verify Your Username\u00a0<\/strong><\/summary>\n<p id=\"htoc-2-verify-your-username\">Your username must be your&nbsp;<strong>full email address<\/strong>.&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-correct-name-yourdomain-co-za\">Correct:&nbsp;<a href=\"mailto:name@yourdomain.co.za\" target=\"_blank\" rel=\"noreferrer noopener\">name@yourdomain.co.za<\/a>&nbsp;<\/li>\n\n\n\n<li id=\"htoc-incorrect-name\">Incorrect:&nbsp;name&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-update-this-in\">Update this in:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Email App \u2192 Account Settings \u2192 <strong><a href=\"https:\/\/1grid.co.za\/knowledge\/recommended-server-settings-for-email-encryption-ports\/#htoc-recommended-secure-email-settings\" target=\"_blank\" rel=\"noreferrer noopener\">Outgoing Server (SMTP)<\/a>\u00a0<\/strong><\/li>\n<\/ul>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>3: Check Your Password\u00a0<\/strong><\/summary>\n<ul class=\"wp-block-list\">\n<li>Re-enter the password carefully\u00a0<\/li>\n\n\n\n<li>Avoid copy\/paste errors\u00a0<\/li>\n\n\n\n<li>Check Caps Lock\u00a0<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-step-3-check-your-password1\">If unsure, <strong><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=reset+password&amp;ht-kb-search=1&amp;lang=\">reset the email password in your\u00a0hosting control panel<\/a>\u00a0<\/strong>and <a href=\"https:\/\/1grid.co.za\/knowledge\/settings-to-configure-your-1grid-email-accounts-across-devices\/\"><strong>update it on all devices<\/strong><\/a>.\u00a0<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>4: Enable SMTP Authentication\u00a0<\/strong><\/summary>\n<p id=\"htoc-4-enable-smtp-authentication\">In your <a href=\"https:\/\/1grid.co.za\/knowledge\/recommended-server-settings-for-email-encryption-ports\/#htoc-recommended-secure-email-settings\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>outgoing mail settings<\/strong><\/a>:\u00a0<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-authentication-must-be-enabled\">Authentication must be enabled&nbsp;<\/li>\n\n\n\n<li id=\"htoc-choose-use-same-credentials-as-incoming-mail-server\">Choose \u201cUse same credentials as incoming mail server\u201d&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-4-enable-smtp-authentication1\">If authentication is disabled, the server will reject the connection.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>5: Confirm SSL\/TLS\u00a0and\u00a0Port Settings\u00a0<\/strong><\/summary>\n<p id=\"htoc-5-confirm-ssl-tls-and-port-settings\">Use\u00a0<a href=\"https:\/\/1grid.co.za\/knowledge\/recommended-server-settings-for-email-encryption-ports\/#htoc-recommended-secure-email-settings\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>secure SMTP settings<\/strong><\/a>:\u00a0<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Setting<\/strong>&nbsp;<\/td><td><strong>Value<\/strong>&nbsp;<\/td><\/tr><tr><td><a href=\"https:\/\/1grid.co.za\/knowledge\/understanding-smtp-ports-and-ssltls-encryption\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Encryption\u00a0<\/strong><\/a><\/td><td>SSL\/TLS&nbsp;<\/td><\/tr><tr><td><a href=\"https:\/\/1grid.co.za\/knowledge\/understanding-smtp-ports-and-ssltls-encryption\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Port\u00a0<\/strong><\/a><\/td><td>465&nbsp;<\/td><\/tr><tr><td>Alternative Port&nbsp;<\/td><td>587 (STARTTLS)&nbsp;<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p id=\"htoc-5-confirm-ssl-tls-and-port-settings1\">If encryption is disabled, authentication may fail.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>6: Restart the Email Application\u00a0<\/strong><\/summary>\n<p id=\"htoc-6-restart-the-email-application\">After saving changes:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Send a test email\u00a0<\/li>\n\n\n\n<li>Close the app completely\u00a0<\/li>\n\n\n\n<li>Reopen it\u00a0<\/li>\n<\/ul>\n<\/details>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-quick-fixes-for-common-smtp-535-variations\"><strong>Quick Fixes for Common SMTP 535 Variations<\/strong>&nbsp;<\/h2>\n\n\n\n<p>SMTP 535 errors are authentication failures. They occur when the mail server cannot verify your login credentials while sending.\u00a0<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>1. 535 Authentication Failed\u00a0<\/strong><\/summary>\n<p id=\"htoc-1-535-authentication-failed\"><strong>What It Means:<\/strong>&nbsp;<br>The username or password used for SMTP login is incorrect.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-how-to-fix-it\"><strong>How to Fix It:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-re-enter-your-password-carefully\">Re-enter your password carefully&nbsp;<\/li>\n\n\n\n<li id=\"htoc-ensure-you-are-using-your-full-email-address-as-the-username\">Ensure you are using your&nbsp;<strong>full email address<\/strong>&nbsp;as the username&nbsp;<\/li>\n\n\n\n<li id=\"htoc-reset-the-mailbox-password-in-your-hosting-control-panel-if-unsure\">Reset the mailbox password in your hosting control panel if unsure&nbsp;<\/li>\n\n\n\n<li id=\"htoc-update-the-password-on-all-connected-devices\">Update the password on all connected devices&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-1-535-authentication-failed1\"><strong>Why It Happens:<\/strong>&nbsp;<br>Incorrect password, outdated saved credentials, or typing errors.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>2. 535 5.7.8 Username and Password Not Accepted\u00a0<\/strong><\/summary>\n<p id=\"htoc-2-535-5-7-8-username-and-password-not-accepted\"><strong>What It Means:<\/strong>&nbsp;<br>The server rejected the login&nbsp;attempt&nbsp;due to invalid credentials or authentication settings.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-how-to-fix-it1\"><strong>How to Fix It:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-confirm-smtp-authentication-is-enabled\">Confirm SMTP authentication is enabled&nbsp;<\/li>\n\n\n\n<li id=\"htoc-verify-port-465-ssl-or-587-tls-is-being-used\">Verify port 465 (SSL) or 587 (TLS) is being used&nbsp;<\/li>\n\n\n\n<li id=\"htoc-check-that-encryption-is-enabled\">Check that encryption is enabled&nbsp;<\/li>\n\n\n\n<li id=\"htoc-reset-the-mailbox-password-and-retry\">Reset the mailbox password and retry&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-2-535-5-7-8-username-and-password-not-accepted1\"><strong>Why It Happens:<\/strong>&nbsp;<br>Authentication is disabled in the email app, the wrong port, or the incorrect encryption settings.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>3. 535 Incorrect Authentication Data\u00a0<\/strong><\/summary>\n<p id=\"htoc-3-535-incorrect-authentication-data\"><strong>What It Means:<\/strong>&nbsp;<br>The login information sent to the server is malformed or incomplete.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-how-to-fix-it11\"><strong>How to Fix It:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-ensure-username-is-the-full-email-address\">Ensure username is the full email address&nbsp;<\/li>\n\n\n\n<li id=\"htoc-remove-extra-spaces-before-or-after-the-username\">Remove extra spaces before or after the username&nbsp;<\/li>\n\n\n\n<li id=\"htoc-re-save-the-account-settings\">Re-save the account settings&nbsp;<\/li>\n\n\n\n<li id=\"htoc-restart-the-email-application\">Restart the email application&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-3-535-incorrect-authentication-data1\"><strong>Why It Happens:<\/strong>&nbsp;<br>Incorrect username format or corrupted account configuration.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>4. 535 Too Many Authentication Failures\u00a0<\/strong><\/summary>\n<p id=\"htoc-4-535-too-many-authentication-failures\"><strong>What It Means:<\/strong>&nbsp;<br>The mailbox has been temporarily locked after multiple failed login attempts.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-how-to-fix-it111\"><strong>How to Fix It:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-wait-15-30-minutes-before-retrying\">Wait 15\u201330 minutes before retrying&nbsp;<\/li>\n\n\n\n<li id=\"htoc-reset-the-mailbox-password\">Reset the mailbox password&nbsp;<\/li>\n\n\n\n<li id=\"htoc-update-credentials-on-all-devices-phone-laptop-tablet\">Update credentials on all devices (phone, laptop, tablet)&nbsp;<\/li>\n\n\n\n<li id=\"htoc-restart-your-router-if-ip-based-lockout-is-suspected\">Restart your router if an IP-based lockout is suspected\u00a0<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-4-535-too-many-authentication-failures1\"><strong>Why It Happens:<\/strong>&nbsp;<br>Repeated incorrect password attempts from one or multiple devices.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>5. 535 Authentication Credentials Invalid (Third-Party Apps)\u00a0<\/strong><\/summary>\n<p id=\"htoc-5-535-authentication-credentials-invalid-third-party-apps\"><strong>What It Means:<\/strong>&nbsp;<br>An application (Outlook, Thunderbird, phone mail app, website plugin) is using outdated or incorrect SMTP credentials.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-how-to-fix-it1111\"><strong>How to Fix It:<\/strong>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-update-stored-credentials-in-the-application\">Update stored credentials in the application&nbsp;<\/li>\n\n\n\n<li id=\"htoc-remove-and-re-add-the-email-account\">Remove and re-add the email account&nbsp;<\/li>\n\n\n\n<li id=\"htoc-confirm-correct-outgoing-mail-server-hostname\">Confirm the correct outgoing mail server hostname&nbsp;<\/li>\n\n\n\n<li id=\"htoc-test-sending-after-updating\">Test sending after updating&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-5-535-authentication-credentials-invalid-third-party-apps1\"><strong>Why It Happens:<\/strong>&nbsp;<br>The password was changed in the hosting panel, but not updated in the email client.&nbsp;<\/p>\n<\/details>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-advanced-optional-fixes-for-technical-users\"><strong>Advanced (Optional) Fixes (For Technical Users)<\/strong>&nbsp;<\/h2>\n\n\n\n<p>Administrators, Developers or Technical Users can diagnose SMTP authentication failures, SASL configuration issues, and credential validation errors.&nbsp;<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>1. Check Mail Server Logs\u00a0<\/strong><\/summary>\n<p id=\"htoc-1-check-mail-server-logs\">SMTP 535 errors are logged during the authentication phase.&nbsp;<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Exim (cPanel\/WHM)&nbsp;<\/strong><\/summary>\n<pre id=\"htoc-exim-cpanel-whm\" class=\"wp-block-code\"><code>grep \"535\" \/var\/log\/exim_mainlog&nbsp;\ntail -f \/var\/log\/exim_mainlog&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-look-for-entries-such-as\">Look for entries such as:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-exim-cpanel-whm1\" class=\"wp-block-code\"><code>authentication failed&nbsp;\n535 Incorrect authentication data&nbsp;\n535 5.7.8 Username and Password not accepted&nbsp;<\/code><\/pre>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Postfix&nbsp;<\/strong><\/summary>\n<pre id=\"htoc-postfix\" class=\"wp-block-code\"><code>grep \"sasl\" \/var\/log\/maillog&nbsp;\ngrep \"authentication failed\" \/var\/log\/maillog&nbsp;\ntail -f \/var\/log\/maillog&nbsp;<\/code><\/pre>\n<\/details>\n\n\n\n<p id=\"htoc-1-check-mail-server-logs1\"><strong>Goal:<\/strong>&nbsp;<br>Confirm whether the failure is due to invalid credentials, disabled authentication, or SASL misconfiguration.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>2. Verify SASL Authentication is Enabled\u00a0<\/strong><\/summary>\n<p id=\"htoc-2-verify-sasl-authentication-is-enabled\">SMTP 535 often occurs when <a href=\"https:\/\/en.wikipedia.org\/wiki\/Simple_Authentication_and_Security_Layer\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SASL authentication<\/strong> <\/a>is disabled or misconfigured.\u00a0<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Postfix \u2013 Check Main Configuration\u00a0<\/strong><\/summary>\n<pre id=\"htoc-postfix-check-main-configuration\" class=\"wp-block-code\"><code>cat \/etc\/postfix\/main.cf | grep&nbsp;smtpd_sasl_auth_enable&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-ensure-this-shows\">Ensure this shows:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-smtpd-sasl-auth-enable-yes\">smtpd_sasl_auth_enable&nbsp;= yes&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-also-verify\">Also verify:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-smtpd-sasl-security-options\">smtpd_sasl_security_options&nbsp;<\/li>\n\n\n\n<li id=\"htoc-smtpd-recipient-restrictions\">smtpd_recipient_restrictions&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-restart-postfix-after-changes\">Restart Postfix after changes:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-postfix-check-main-configuration1\" class=\"wp-block-code\"><code>systemctl&nbsp;restart postfix&nbsp;<\/code><\/pre>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Exim \u2013 Confirm Authentication Drivers&nbsp;<\/strong><\/summary>\n<p id=\"htoc-exim-confirm-authentication-drivers\">Review the authentication section:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-nano-etc-exim-conf\" class=\"wp-block-code\"><code>nano \/etc\/exim.conf&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-ensure-authenticators-are-enabled-e-g-plain-login\">Ensure authenticators are enabled (e.g.,&nbsp;plain,&nbsp;login).&nbsp;<\/p>\n\n\n\n<p id=\"htoc-restart-exim-if-adjustments-are-made\">Restart Exim if adjustments are made:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-exim-confirm-authentication-drivers1\" class=\"wp-block-code\"><code>systemctl&nbsp;restart&nbsp;exim&nbsp;<\/code><\/pre>\n<\/details>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>3. Test SMTP Authentication Manually\u00a0<\/strong><\/summary>\n<p id=\"htoc-3-test-smtp-authentication-manually\">Use<strong> <a href=\"https:\/\/learn.microsoft.com\/en-us\/windows-server\/administration\/windows-commands\/telnet\" target=\"_blank\" rel=\"noreferrer noopener\">Telnet<\/a><\/strong><a href=\"https:\/\/learn.microsoft.com\/en-us\/windows-server\/administration\/windows-commands\/telnet\"> <\/a>or <strong><a href=\"https:\/\/www.openssl.org\/\" target=\"_blank\" rel=\"noreferrer noopener\">OpenSSL<\/a> <\/strong>to test authentication.\u00a0<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Test STARTTLS (Port 587)&nbsp;<\/strong><\/summary>\n<pre id=\"htoc-test-starttls-port-587\" class=\"wp-block-code\"><code>openssl&nbsp;s_client&nbsp;-starttls&nbsp;smtp -connect mail.example.com:587&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-then-manually-issue\">Then manually issue:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-ehlo-yourdomain-com\">EHLO yourdomain.com&nbsp;<\/li>\n\n\n\n<li id=\"htoc-auth-login\">AUTH LOGIN&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-enter-the-base64-encoded-username-and-password\">Enter the <a href=\"https:\/\/www.base64decode.org\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>base64-encoded<\/strong><\/a> username and password.\u00a0<\/p>\n\n\n\n<p id=\"htoc-when-the-server-responds-with\">When the&nbsp;server responds with:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-535-authentication-failed1\" class=\"wp-block-code\"><code>535 Authentication failed&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-test-starttls-port-5871\">Credentials or authentication&nbsp;configs&nbsp;are incorrect.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Test with&nbsp;Swaks&nbsp;<\/strong><\/summary>\n<pre id=\"htoc-test-with-swaks\" class=\"wp-block-code\"><code>swaks&nbsp;--to&nbsp;<a href=\"mailto:test@example.com\" target=\"_blank\" rel=\"noreferrer noopener\">test@example.com<\/a>&nbsp;\\&nbsp;\n--from&nbsp;<a href=\"mailto:sender@yourdomain.com\" target=\"_blank\" rel=\"noreferrer noopener\">sender@yourdomain.com<\/a>&nbsp;\\&nbsp;\n--server mail.yourdomain.com \\&nbsp;\n--auth LOGIN \\&nbsp;\n--auth-user&nbsp;<a href=\"mailto:sender@yourdomain.com\" target=\"_blank\" rel=\"noreferrer noopener\">sender@yourdomain.com<\/a>&nbsp;\\&nbsp;\n--auth-password 'password'&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-test-with-swaks1\">This provides clear&nbsp;authentication&nbsp;success\/failure output.&nbsp;<\/p>\n<\/details>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>4. Verify Mailbox Credentials at System Level\u00a0<\/strong><\/summary>\n<p id=\"htoc-4-verify-mailbox-credentials-at-system-level\">If using virtual mail users, confirm the mailbox exists:&nbsp;<\/p>\n\n\n\n<p id=\"htoc-for-cpanel-check-via-whm-email-accounts\"><strong>For cPanel:\u00a0<\/strong><br>Check via WHM \u2192 Email Accounts\u00a0<\/p>\n\n\n\n<p id=\"htoc-for-postfix-dovecot-setups\"><strong>For Postfix + Dovecot Setups:\u00a0<\/strong><\/p>\n\n\n\n<pre id=\"htoc-cat-etc-dovecot-users\" class=\"wp-block-code\"><code>cat \/etc\/dovecot\/users&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-if-password-hashes-are-used-confirm-they-match-the-expected-authentication-method\">If password hashes are used, confirm they match&nbsp;the expected&nbsp;authentication method.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-4-verify-mailbox-credentials-at-system-level1\">Reset the mailbox password and retest if needed.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>5. Check for Account Lockouts or Rate Limits\u00a0<\/strong><\/summary>\n<p id=\"htoc-5-check-for-account-lockouts-or-rate-limits\">Multiple failed login attempts can trigger temporary locks.\u00a0<\/p>\n\n\n\n<p id=\"htoc-check-logs-for\">Check logs for:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-too-many-login-attempts\">Too many&nbsp;login&nbsp;attempts&nbsp;<\/li>\n\n\n\n<li id=\"htoc-authentication-temporarily-blocked\">Authentication temporarily blocked&nbsp;<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-if-present\">If present:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Reset password\u00a0<\/li>\n\n\n\n<li>Wait 15 to 30 minutes\u00a0<\/li>\n\n\n\n<li>Restart mail services if necessary\u00a0<\/li>\n<\/ul>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>6. Confirm Correct Ports and Encryption\u00a0<\/strong><\/summary>\n<p id=\"htoc-6-confirm-correct-ports-and-encryption\">Authentication failures can occur if SSL\/TLS is mismatched.&nbsp;<\/p>\n\n\n\n<p id=\"htoc-verify\">Verify:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-port-465-ssl\">Port 465 \u2192 SSL&nbsp;<\/li>\n\n\n\n<li id=\"htoc-port-587-starttls\">Port 587 \u2192 STARTTLS&nbsp;<\/li>\n\n\n\n<li id=\"htoc-encryption-is-enabled-in-client\">Encryption is enabled in the mail client\u00a0<\/li>\n<\/ul>\n\n\n\n<p id=\"htoc-test-listening-ports\">Test&nbsp;listening&nbsp;ports:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-netstat-tlnp-grep-465-netstat-tlnp-grep-587\" class=\"wp-block-code\"><code>netstat -tlnp&nbsp;| grep :465&nbsp;<br>netstat -tlnp&nbsp;| grep :587&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-6-confirm-correct-ports-and-encryption1\">If ports are closed, check&nbsp;firewall&nbsp;rules.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>7. Check Firewall or Security Modules\u00a0<\/strong><\/summary>\n<p id=\"htoc-7-check-firewall-or-security-modules\">Security systems (<a href=\"https:\/\/www.checkpoint.com\/cyber-hub\/cloud-security\/what-is-web-application-firewall\/what-is-a-cloud-security-framework-csf\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>CSF<\/strong><\/a>, <a href=\"https:\/\/www.plesk.com\/blog\/various\/using-fail2ban-to-secure-your-server\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Fail2Ban<\/strong><\/a>,<strong>\u00a0<a href=\"https:\/\/github.com\/owasp-modsecurity\/ModSecurity\" target=\"_blank\" rel=\"noreferrer noopener\">ModSecurity<\/a><\/strong>) may block repeated attempts.\u00a0<\/p>\n\n\n\n<p id=\"htoc-for-csf\">For CSF:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-csf-g-lt-client-ip-gt\" class=\"wp-block-code\"><code>csf&nbsp;-g &lt;client-ip&gt;&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-unblock-if-necessary\">Unblock if necessary:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-csf-dr-lt-client-ip-gt\" class=\"wp-block-code\"><code>csf&nbsp;-dr &lt;client-ip&gt;&nbsp;<\/code><\/pre>\n\n\n\n<p id=\"htoc-review-fail2ban\">Review Fail2Ban:&nbsp;<\/p>\n\n\n\n<pre id=\"htoc-7-check-firewall-or-security-modules1\" class=\"wp-block-code\"><code>fail2ban-client status\u00a0<\/code><\/pre>\n<\/details>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-before-you-move-on\"><strong>Before You Move&nbsp;On<\/strong><strong>&nbsp;<\/strong>&nbsp;<\/h2>\n\n\n\n<p id=\"htoc-\">Ask yourself:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-did-you-update-the-password-on-every-device\">Did you update the password on\u00a0<strong>every device<\/strong>?\u00a0<\/li>\n\n\n\n<li id=\"htoc-are-you-using-the-full-email-address-as-username\">Are you using the full email address as\u00a0a username?\u00a0<\/li>\n\n\n\n<li id=\"htoc-is-authentication-enabled\">Is authentication enabled?\u00a0<\/li>\n<\/ul>\n\n\n\n<p>Most 535 errors are resolved by correcting one of these three items.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-if-this-didn-t-work\"><strong>If This&nbsp;Didn\u2019t&nbsp;Work<\/strong>&nbsp;<\/h2>\n\n\n\n<p>If the error continues:&nbsp;<\/p>\n\n\n\n<ol start=\"1\" class=\"wp-block-list\">\n<li id=\"htoc-check-if-your-hosting-account-is-active\">Check if your hosting account is active\u00a0<\/li>\n\n\n\n<li id=\"htoc-ensure-the-mailbox-is-not-suspended1\">Ensure the mailbox is not suspended\u00a0<\/li>\n\n\n\n<li id=\"htoc-confirm-you-are-not-exceeding-sending-limits\">Confirm you are not exceeding sending limits\u00a0<\/li>\n\n\n\n<li id=\"htoc-remove-and-re-add-the-account-in-your-email-app\">Remove and re-add the account in your email app\u00a0<\/li>\n\n\n\n<li id=\"htoc-test-sending-via-webmail\">Test sending via Webmail\u00a0<\/li>\n<\/ol>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\"><\/ol>\n\n\n\n<ol start=\"3\" class=\"wp-block-list\"><\/ol>\n\n\n\n<ol start=\"4\" class=\"wp-block-list\"><\/ol>\n\n\n\n<ol start=\"5\" class=\"wp-block-list\"><\/ol>\n\n\n\n<p>If <strong><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-access-your-email-via-webmail\/\" target=\"_blank\" rel=\"noreferrer noopener\">Webmail<\/a> <\/strong>works but your app\u00a0doesn\u2019t\u00a0\u2192 the issue is local to the device.\u00a0<\/p>\n\n\n\n<p>If<strong> <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-access-your-email-via-webmail\/\" target=\"_blank\" rel=\"noreferrer noopener\">Webmail<\/a><\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-access-your-email-via-webmail\/\"> <\/a>also fails \u2192 contact Support.\u00a0<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-common-mistakes-to-avoid\"><strong>Common Mistakes to Avoid<\/strong>&nbsp;<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-changing-the-password-but-not-updating-mobile-devices\">Changing the password but not updating mobile devices\u00a0<\/li>\n\n\n\n<li id=\"htoc-disabling-ssl-because-it-worked-before\">Disabling SSL because \u201cit worked before\u201d\u00a0<\/li>\n\n\n\n<li id=\"htoc-using-old-saved-credentials\">Using\u00a0old saved\u00a0credentials\u00a0<\/li>\n\n\n\n<li id=\"htoc-mixing-pop-and-imap-settings\">Mixing POP and IMAP settings\u00a0<\/li>\n\n\n\n<li id=\"htoc-leaving-smtp-authentication-unchecked\">Leaving SMTP authentication unchecked\u00a0<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-empowering-insight\"><strong>Empowering Insight<\/strong>&nbsp;<\/h2>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1600\" height=\"300\" src=\"https:\/\/1grid.co.za\/knowledge\/wp-content\/uploads\/2026\/03\/1-grid-Images-for-KB-Articles-1000-x-600-px-1600-x-300-px.png\" alt=\"Empowering Insight\" class=\"wp-image-34464\"\/><\/figure>\n<\/div>\n\n\n<p>If Webmail works, your server is working.&nbsp;<\/p>\n\n\n\n<p>When Webmail succeeds, and your app fails, the issue is\u00a0almost always\u00a0a local configuration setting, and not a hosting problem.\u00a0<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-next-recommended-steps\"><strong>Next Recommended Steps<\/strong>&nbsp;<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-reset-email-password\"><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=email+password&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\">Reset the Email Password<\/a>\u00a0<\/strong><\/li>\n\n\n\n<li id=\"htoc-verify-smtp-settings\"><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/recommended-server-settings-for-email-encryption-ports\/#htoc-recommended-secure-email-settings\" target=\"_blank\" rel=\"noreferrer noopener\">Verify SMTP Settings<\/a>\u00a0<\/strong><\/li>\n\n\n\n<li id=\"htoc-review-sending-limits\"><a href=\"https:\/\/1grid.co.za\/knowledge\/email-restrictions\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Review Sending Limits\u00a0<\/strong><\/a><\/li>\n\n\n\n<li id=\"htoc-secure-all-connected-devices\">Secure All Connected Devices\u00a0<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-faqs\"><strong>FAQs<\/strong>&nbsp;<\/h2>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q.\u00a0Why did this suddenly start happening?\u00a0<\/strong><\/summary>\n<p id=\"htoc-q-why-did-this-suddenly-start-happening-most-commonly\">Most commonly:\u00a0<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Password change\u00a0<\/li>\n\n\n\n<li>New device setup\u00a0<\/li>\n\n\n\n<li>Security update enforcing SSL<\/li>\n<\/ul>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q.\u00a0Can repeated SMTP error 535 bounce backs lock my account?\u00a0<\/strong><\/summary>\n<p id=\"htoc-q-can-repeated-smtp-error-535-lock-my-account-yes-excessive-failed-attempts-can-trigger-temporary-restrictions\">Yes, excessive failed attempts can trigger temporary restrictions.<\/p>\n<\/details>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-additional-resources\"><strong>Additional&nbsp;Resources<\/strong>&nbsp;<\/h2>\n\n\n\n<p><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/a-guide-to-smtperror-codes\/\" target=\"_blank\" rel=\"noreferrer noopener\">SMTP Error Codes<\/a>\u00a0\u00a0<\/strong><br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SPF\/DKIM Setup Guide\u00a0\u00a0<\/strong><\/a><br><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/email-restrictions\/\" target=\"_blank\" rel=\"noreferrer noopener\">Email Sending Limits Guide\u00a0<\/a>\u00a0<\/strong><br><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=email+password&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\">Updating Your Email Password\u00a0<\/a>\u00a0<\/strong><br><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=outlook&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\">Troubleshooting Outlook Errors\u00a0<\/a>\u00a0<\/strong><br><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/why-emails-bounce-back-error-messages-and-how-to-fix-them\" target=\"_blank\" rel=\"noreferrer noopener\">Email Bounce Back Guide<\/a>\u00a0<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-need-additional-support\"><strong>Need Additional Support?<\/strong>&nbsp;<\/h2>\n\n\n\n<p><strong>We&#8217;re&nbsp;Here to&nbsp;<\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Help<\/strong><\/a><strong>:<\/strong>&nbsp;<\/p>\n\n\n\n<p>Understanding SMTP Error 535 and how to fix this&nbsp;doesn\u2019t&nbsp;have&nbsp;to&nbsp;feel technical&nbsp;with&nbsp;this&nbsp;easy-to-reference guide. Stuck?&nbsp;Check out our&nbsp;<a href=\"https:\/\/1grid.co.za\/knowledge\/1-grid-scope-of-support\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Scope of Support<\/strong><\/a>, and then contact our Support Team for&nbsp;further&nbsp;clarity and&nbsp;guidance&nbsp;(<a href=\"https:\/\/1grid.co.za\/contact-us\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>https:\/\/1grid.co.za\/contact-us\/<\/strong><\/a>).&nbsp;We&#8217;re&nbsp;ready&nbsp;to see&nbsp;how we can help!&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>If\u00a0you&#8217;re\u00a0seeing\u00a0SMTP Error 535: Authentication Failed, your email client cannot log into the outgoing mail server.\u00a0 This&nbsp;guide will help you:&nbsp; Nothing in this process will affect your website, hosting, or existing mail data.&nbsp; By the end of this guide,&nbsp;you\u2019ll&nbsp;confidently resolve SMTP 535 errors without contacting support.&nbsp; What SMTP Error 535 Means&nbsp;&#8230;<\/p>\n","protected":false},"author":21,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"ht-kb-category":[1194],"ht-kb-tag":[1723,1719,1720,1721,1494,1707,1514,1718,1706,1701],"class_list":["post-34539","ht_kb","type-ht_kb","status-publish","format-standard","hentry","ht_kb_category-email-troubleshooting","ht_kb_tag-535-5-7-8-esmtp-error-code","ht_kb_tag-535-authentication-failed","ht_kb_tag-535-incorrect-authentication-data","ht_kb_tag-535-username-and-password-not-accepted","ht_kb_tag-email-configuration","ht_kb_tag-email-delivery-issues","ht_kb_tag-email-troubleshooting","ht_kb_tag-smtp-535-fix","ht_kb_tag-smtp-bounce-errors","ht_kb_tag-smtp-errors"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>SMTP Error 535: Authentication Failed (How to Fix It) - 1-grid Knowledge Base<\/title>\n<meta name=\"description\" content=\"Fix SMTP Error 535 authentication failed. 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