{"id":24033,"date":"2025-10-16T11:36:18","date_gmt":"2025-10-16T11:36:18","guid":{"rendered":"https:\/\/1-grid.com\/knowledge\/how-to-resolve-mailchannels-error-550-too-many-invalid-recipients\/"},"modified":"2025-10-16T11:36:57","modified_gmt":"2025-10-16T11:36:57","slug":"how-to-resolve-mailchannels-error-550-too-many-invalid-recipients","status":"publish","type":"ht_kb","link":"https:\/\/1grid.co.za\/knowledge\/how-to-resolve-mailchannels-error-550-too-many-invalid-recipients\/","title":{"rendered":"Resolving a MailChannels \u201c550 5.7.1 [IRR] Too Many Invalid Recipients\u201d Error"},"content":{"rendered":"\n<p>If you see a \u201c<strong>550 5.7.1 [IRR] Too Many Invalid Recipients<\/strong>\u201d error when sending an email, don\u2019t worry! It\u2019s a temporary protection measure from <a href=\"https:\/\/www.mailchannels.com\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>MailChannels<\/strong><\/a>, our outbound firewall partner, helping to keep your domain\u2019s reputation strong by preventing your emails from being flagged as spam.&nbsp;&nbsp;<\/p>\n\n\n\n<p>&nbsp;In this guide, we\u2019ll show you exactly what it means, how to fix it, and what to do to prevent it from happening again.&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\/2022\/02\/1-grid-Images-for-KB-Articles-1000-x-600-px-53.png\" alt=\"\" class=\"wp-image-33825\"\/><\/figure>\n<\/div>\n\n\n<div class=\"wp-block-ht-block-toc is-style-rounded 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 Does The 550 5.7.1 [IRR] Error Mean?<\/a><\/li><li class=\"\"><a href=\"#htoc-1\">Why MailChannels Blocks These Emails&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-11\">How to Fix the Error&nbsp;<\/a><ul class=\"ht_toc_child_list\"><li class=\"\"><a href=\"#htoc-1-clean-your-mailing-list\">1: Clean Your Mailing List&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-2-enable-double-opt-in\">2: Enable Double Opt-In&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-3-send-only-to-active-subscribers\">3: Send Only to Active Subscribers&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-4-wait-for-automatic-unblock\">4: Wait for Automatic Unblock&nbsp;<\/a><\/li><\/ul><\/li><li class=\"\"><a href=\"#htoc-11111111\">Tips to Reduce Flags and Maintain a Healthy Sender Reputation&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-111111111\">How to Prevent Future Blocks&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-111111111111\">When to Contact 1-grid Support&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-111111111111111\">FAQs&nbsp;&nbsp;<\/a><\/li><li class=\"\"><a href=\"#htoc-1111111111111111\">Additional Resources&nbsp;<\/a><\/li><\/ul><\/div><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-\"><strong>What Does The 550 5.7.1 [IRR] Error Mean?<\/strong><\/h2>\n\n\n\n<p>This error indicates that your account sent messages to a <strong>large number of invalid email addresses<\/strong> which means you\u2019re trying to send to recipients that no longer exist or have incorrect formats.&nbsp;<\/p>\n\n\n\n<p>MailChannels automatically pauses outgoing mail to <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-avoid-mailchannels-blocks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>prevent reputation damage<\/strong><\/a> and potential blacklisting of your domain or server IP.&nbsp;&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-1\"><strong>Why MailChannels Blocks These Emails&nbsp;<\/strong><\/h2>\n\n\n\n<p>MailChannels uses advanced filtering and behaviour-based algorithms to detect potential<strong> <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-avoid-mailchannels-blocks\/\" target=\"_blank\" rel=\"noreferrer noopener\">spam-like patterns<\/a><\/strong>.&nbsp;<\/p>\n\n\n\n<p>Sending to invalid addresses is a strong indicator of:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-outdated-or-unverified-mailing-lists\">Outdated or <strong><a href=\"https:\/\/learn.microsoft.com\/en-us\/answers\/questions\/4709404\/how-to-turn-off-unverified-sender-block-on-individ\" target=\"_blank\" rel=\"noreferrer noopener\">unverified mailing lists<\/a>&nbsp;<\/strong><\/li>\n\n\n\n<li id=\"htoc-11111111111111111\">Bulk mailings without confirmed recipients&nbsp;<\/li>\n\n\n\n<li id=\"htoc-111111111111111111\"><strong><a href=\"https:\/\/1grid.co.za\/knowledge\/settings-to-configure-your-1grid-email-accounts-across-devices\/\" target=\"_blank\" rel=\"noreferrer noopener\">Misconfigured third-party mailing tools<\/a><\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong>IMPORTANT:<\/strong> High volumes of invalid recipients can damage your domain\u2019s <strong>email reputation<\/strong>, increasing the risk that valid emails will land in <strong><a href=\"https:\/\/1grid.co.za\/knowledge\/blocked-via-mailchannels-due-to-spam\/\" target=\"_blank\" rel=\"noreferrer noopener\">spam<\/a> <\/strong>or get <strong><a href=\"https:\/\/1grid.co.za\/knowledge\/mailchannels-errors-codes\/\" target=\"_blank\" rel=\"noreferrer noopener\">blocked<\/a> <\/strong>entirely.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-11\"><strong>How to Fix the Error&nbsp;<\/strong><\/h2>\n\n\n\n<p>To resolve the block and restore your email sending, follow these steps carefully:&nbsp;<\/p>\n\n\n\n<h6 class=\"wp-block-heading\" id=\"htoc-1-clean-your-mailing-list\"><strong><em>1: Clean Your Mailing List<\/em><\/strong>&nbsp;<\/h6>\n\n\n\n<p>Use email verification tools to identify and remove invalid recipients:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-verifyemailaddress-org\"><strong><a href=\"https:\/\/www.verifyemailaddress.org\/\" target=\"_blank\" rel=\"noreferrer noopener\">VerifyEmailAddress.org<\/a>&nbsp;<\/strong><\/li>\n\n\n\n<li id=\"htoc-111\"><strong><a href=\"https:\/\/mailtester.com\/testmail.php\" target=\"_blank\" rel=\"noreferrer noopener\">MailTester.com<\/a>&nbsp;<\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong>IMPORTANT: <\/strong>Delete all invalid or bounced addresses before resending.&nbsp;<\/p>\n\n\n\n<h6 class=\"wp-block-heading\" id=\"htoc-2-enable-double-opt-in\"><strong><em>2: Enable Double Opt-In<\/em><\/strong>&nbsp;<\/h6>\n\n\n\n<p>Implement <a href=\"https:\/\/customer.io\/learn\/deliverability\/double-opt-in-best-practices\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>double opt-in<\/strong><\/a> on your contact forms or subscription lists. This means new subscribers confirm their email address before being added, ensuring every contact is valid.&nbsp;<\/p>\n\n\n\n<h6 class=\"wp-block-heading\" id=\"htoc-3-send-only-to-active-subscribers\"><strong><em>3: Send Only to Active Subscribers<\/em><\/strong>&nbsp;<\/h6>\n\n\n\n<p>Only send to verified, opted-in addresses. Avoid purchased or scraped lists and re-engage inactive users before sending bulk messages.&nbsp;<\/p>\n\n\n\n<h6 class=\"wp-block-heading\" id=\"htoc-4-wait-for-automatic-unblock\"><strong><em>4: Wait for Automatic Unblock<\/em><\/strong>&nbsp;<\/h6>\n\n\n\n<p>Once your mailing list is cleaned, MailChannels typically <strong>lifts the block automatically<\/strong> within a few hours once normal sending behaviour resumes.&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-check-the-content-remove-spammy-phrases-suspicious-links-or-large-attachments\"><strong>Check the content<\/strong>: Remove <a href=\"https:\/\/www.activecampaign.com\/blog\/spam-words\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>spammy phrases<\/strong><\/a>, <a href=\"https:\/\/easydmarc.com\/tools\/phishing-url\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>suspicious links<\/strong><\/a>, or large attachments.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-1111\"><strong>Authenticate your domain<\/strong>: Add <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\"><strong>SPF<\/strong><\/a>,<strong> <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\">DKIM<\/a><\/strong>, and <a href=\"https:\/\/1grid.co.za\/knowledge\/cpanel-how-to-add-dmarc-record\/\"><strong>DMARC<\/strong><\/a><a href=\"https:\/\/1grid.co.za\/knowledge\/understanding-dns-records-and-how-to-check-these\/\"> <strong>records<\/strong><\/a> to validate your email.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-11111\"><strong>Secure your account<\/strong>: <a href=\"https:\/\/1grid.co.za\/knowledge\/?s=change+password&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Change your password<\/strong><\/a>, update your operating system, and run antivirus scans.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-111111\"><strong>Clean your mailing list<\/strong>: Remove invalid addresses or unengaged contacts.<\/li>\n\n\n\n<li id=\"htoc-1111111\"><strong>Retry sending<\/strong>: Once fixes are applied, retry sending the message.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-11111111\"><strong>Tips to Reduce Flags and Maintain a Healthy Sender Reputation&nbsp;<\/strong><\/h2>\n\n\n\n<p>1. <strong>Avoid sending bulk messages too quickly.<\/strong> Space out your emails.&nbsp;<br>2. <strong>Regularly verify and update your contact lists.<\/strong>&nbsp;<br>3. <strong>Authenticate your domain with <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SPF<\/strong><\/a><strong>, <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>DKIM<\/strong><\/a><strong>, and <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/cpanel-how-to-add-dmarc-record\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>DMARC<\/strong><\/a><strong> <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/understanding-dns-records-and-how-to-check-these\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>records<\/strong><\/a><strong>.<\/strong>&nbsp;<br>4. <strong>Monitor <\/strong><a href=\"https:\/\/mailtrap.io\/blog\/email-bounce-rate\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>bounce rates<\/strong><\/a><strong>.<\/strong> Keep them below 2%.&nbsp;<br>5. <strong>Never buy email lists.<\/strong> These lists often contain invalid or spam-trap addresses.&nbsp;<\/p>\n\n\n\n<p><strong>TIP: <\/strong>Monitoring and cleaning your mailing list regularly keeps your email deliverability strong and <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-avoid-mailchannels-blocks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>prevents future blocks<\/strong><\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-111111111\"><strong>How to Prevent Future Blocks&nbsp;<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-1111111111\">Review your email sending patterns every month.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-set-up-spf-dkim-and-dmarc-for-your-domain-to-improve-trust-scores\">Set up <a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SPF<\/strong><\/a><strong>, <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>DKIM<\/strong><\/a><strong>, and <\/strong><a href=\"https:\/\/1grid.co.za\/knowledge\/cpanel-how-to-add-dmarc-record\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>DMARC<\/strong><\/a> for your domain to improve trust scores.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-11111111111\">Avoid attachments or links that could appear <a href=\"https:\/\/1grid.co.za\/knowledge\/blocked-via-mailchannels-due-to-spam\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>suspicious<\/strong><\/a>.&nbsp;<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-111111111111\"><strong>When to Contact 1-grid Support&nbsp;<\/strong><\/h2>\n\n\n\n<p>If you\u2019ve cleaned your mailing list but your emails are still blocked after 24 hours, provide the following (with screenshots, where possible):&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li id=\"htoc-1111111111111\">The full bounce-back message.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-steps-you-ve-already-tried\">Steps you\u2019ve already tried.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-provide-your-sending-email-address-and-timestamp-of-the-error\">Provide your <strong>sending email address<\/strong> and the <strong>timestamp of the error<\/strong>.&nbsp;<\/li>\n\n\n\n<li id=\"htoc-11111111111111\">Our Support team will <strong>review logs<\/strong> and liaise with MailChannels if necessary to unblock your account.&nbsp;<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-111111111111111\"><strong>FAQs&nbsp;&nbsp;<\/strong><\/h2>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: What does \u201c550 Too Many Invalid Recipients\u201d mean?<\/strong>&nbsp;<\/summary>\n<p id=\"htoc-q-what-does-550-too-many-invalid-recipients-mean-it-means-your-account-has-sent-too-many-emails-to-addresses-that-don-t-exist-or-are-invalid-mailchannels-temporarily-blocks-further-sending-to-protect-your-email-reputation\">It means your account has sent too many emails to addresses that don\u2019t exist or are invalid. MailChannels temporarily blocks further sending to protect your email reputation.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: How do I unblock my account?<\/strong>&nbsp;<\/summary>\n<p id=\"htoc-q-how-do-i-unblock-my-account-clean-your-mailing-list-using-verification-tools-remove-invalid-addresses-and-wait-a-few-hours-the-block-usually-lifts-automatically-once-the-issue-is-resolved\">Clean your mailing list using verification tools, remove invalid addresses, and wait a few hours. The block usually lifts automatically once the issue is resolved.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: Why is this important for email deliverability?<\/strong>&nbsp;<\/summary>\n<p id=\"htoc-q-why-is-this-important-for-email-deliverability-invalid-recipients-hurt-your-sender-reputation-causing-legitimate-messages-to-go-to-spam-or-get-blocked-entirely\">Invalid recipients hurt your sender reputation, causing legitimate messages to go to spam or get blocked entirely.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: Can I prevent this from happening again?<\/strong>&nbsp;<\/summary>\n<p id=\"htoc-q-can-i-prevent-this-from-happening-again-yes-by-regularly-cleaning-your-mailing-list-using-double-opt-in-and-avoiding-purchased-lists\">Yes, by regularly cleaning your mailing list, using double opt-in, and avoiding purchased lists.&nbsp;<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: When should I contact support?<\/strong>&nbsp;<\/summary>\n<p id=\"htoc-q-when-should-i-contact-support-if-the-block-doesn-t-lift-after-24-hours-or-if-you-continue-receiving-bounce-errors-despite-list-cleanup\">If the block doesn\u2019t lift after 24 hours, or if you continue receiving bounce errors despite list cleanup.&nbsp;<\/p>\n<\/details>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-1111111111111111\"><strong>Additional Resources&nbsp;<\/strong><\/h2>\n\n\n\n<p><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-avoid-mailchannels-blocks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How to Avoid MailChannels Blocks&nbsp;<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/mailchannels-errors-codes\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>MailChannels Error Codes and How to Fix Them<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/blocked-via-mailchannels-due-to-spam\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Resolving a MailChannels Spam Block \u201c550 5.7.1\u201d Error<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=mailchannels&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>MailChannels FAQs<\/strong><\/a>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=DNS&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Everything You Need to Know About Domain Name Systems (DNS)<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=change+password&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Updating My Password FAQs<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/top-10-common-email-issues-and-how-to-resolve-them\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Top 10 Common Email Issues and How to Resolve Them<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/setting-up-email-in-outlook-via-windows-control-panel\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Setting Up Email in Outlook via Windows Control Panel<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-set-up-email-on-android-for-your-1grid-email-accounts\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How to Set Up Email on Android for Your 1-grid Email Accounts<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/settings-to-configure-your-1grid-email-accounts-across-devices\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Settings to Configure Your 1-grid Email Accounts Across Devices<\/strong><\/a><strong>&nbsp;&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/resolving-email-error-messages-when-sending-to-gmail-accounts\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Resolving Email Error Messages When Sending to Gmail Accounts<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/what-is-ip-blacklisting\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>What is IP Blacklisting?<\/strong><\/a>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-check-if-my-ip-is-blacklisted\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How Do I Check if My IP is Blacklisted?<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/spamtitan-how-to-blacklist-an-email-address-or-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SpamTitan: How to Blacklist an Email Address or Domain<\/strong><\/a>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/what-is-email-spoofing\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>What Is Email Spoofing? How It Works and How to Protect Yourself&nbsp;<\/strong><\/a>&nbsp;&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-spot-a-scam-email\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How to Spot a Scam Email<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=email+headers&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Email Headers FAQs<\/strong><\/a><br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=email&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Email FAQs<\/strong><\/a><br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-enable-dkim-and-spf-on-your-mail-domain\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How to Enable DKIM and SPF on Your Mail Domain<\/strong><\/a><strong>&nbsp;<\/strong>&nbsp;<br><a href=\"https:\/\/1grid.co.za\/knowledge\/why-ssl-the-purpose-of-using-ssl-certificates\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Why SSL? The Purpose of Using SSL Certificates<\/strong><\/a><br><a href=\"https:\/\/1grid.co.za\/knowledge\/what-is-a-domain-name-server-dns\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>What is a Domain Name Server (DNS)?<\/strong><\/a><br><a href=\"https:\/\/1grid.co.za\/knowledge\/how-to-update-your-domains-nameservers-at-1-grid\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>How to Update Your Domain\u2019s Nameservers at 1-grid<\/strong><\/a><strong>&nbsp;<\/strong><br><a href=\"https:\/\/1grid.co.za\/knowledge\/?s=spamtitan&amp;ht-kb-search=1&amp;lang=\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>SpamTitan FAQs<\/strong><\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"htoc-1111111111111111111\"><strong>Need Additional Support?&nbsp;<\/strong><\/h2>\n\n\n\n<p><strong>We&#8217;re Here to <\/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>Preventing emails from being blocked by MailChannels doesn\u2019t have to feel technical with this easy-to-reference guide. Stuck? Contact our Support Team for clarity and guidance (<a href=\"https:\/\/1grid.co.za\/contact-us\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>https:\/\/1grid.co.za\/contact-us\/<\/strong><\/a>). We&#8217;re ready to see how we can help!&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>If you see a \u201c550 5.7.1 [IRR] Too Many Invalid Recipients\u201d error when sending an email, don\u2019t worry! It\u2019s a temporary protection measure from MailChannels, our outbound firewall partner, helping to keep your domain\u2019s reputation strong by preventing your emails from being flagged as spam.&nbsp;&nbsp; &nbsp;In this guide, we\u2019ll show&#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":[1173,1194],"ht-kb-tag":[51,336,1482,369,470,480,537,597,598,609,813,849,1030,1046],"class_list":["post-24033","ht_kb","type-ht_kb","status-publish","format-standard","hentry","ht_kb_category-email","ht_kb_category-email-troubleshooting","ht_kb_tag-51","ht_kb_tag-email","ht_kb_tag-email-errors","ht_kb_tag-error","ht_kb_tag-hosting","ht_kb_tag-how-to","ht_kb_tag-invalid","ht_kb_tag-mailchannel","ht_kb_tag-mailchannels","ht_kb_tag-many","ht_kb_tag-recipients","ht_kb_tag-resolve","ht_kb_tag-too","ht_kb_tag-troubleshooting"],"yoast_head":"<!-- This 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