{"id":5282,"date":"2026-03-12T03:05:05","date_gmt":"2026-03-12T03:05:05","guid":{"rendered":"https:\/\/emailwarmup.com\/blog\/?p=5282"},"modified":"2026-03-12T03:05:06","modified_gmt":"2026-03-12T03:05:06","slug":"how-to-fix-454-4-7-0-tls-not-available","status":"publish","type":"post","link":"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/","title":{"rendered":"How To Fix 454 4.7.0 | TLS Not Available (Encryption Required)"},"content":{"rendered":"\n<figure class=\"wp-block-image size-full\"><img fetchpriority=\"high\" decoding=\"async\" width=\"3448\" height=\"2195\" src=\"https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg\" alt=\"454 4.7.0\" class=\"wp-image-5283\"\/><\/figure>\n\n\n\n<p>The 454 4.7.0 error means the recipient&#8217;s server requires TLS encryption, but your sending server cannot establish a secure connection \u2014 either TLS isn&#8217;t enabled, negotiation failed, or certificate problems blocked the handshake.&nbsp;<\/p>\n\n\n\n<p>Fix it by enabling TLS\/SSL in your email client settings (use port 587 with STARTTLS or port 465 with implicit SSL), verifying credentials, and ensuring your software supports current TLS versions.<\/p>\n\n\n\n<p>TLS (Transport Layer Security) encrypts email in transit, preventing interception. Many servers now <em>require<\/em> encryption \u2014 they reject unencrypted connections outright.&nbsp;<\/p>\n\n\n\n<p>The 454 code signals that the recipient demands TLS, but your side can&#8217;t provide it. Fixing requires configuration changes at the client or server level.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Quick skim \u2014 454 4.7.0 error overview<\/h2>\n\n\n\n<p>The 454 4.7.0 error indicates encryption negotiation failure between sending and receiving servers.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Attribute<\/td><td>Details<\/td><\/tr><tr><td>Error code<\/td><td>454 4.7.0<\/td><\/tr><tr><td>Category<\/td><td>TLS \/ encryption failure<\/td><\/tr><tr><td>Meaning<\/td><td>Recipient requires TLS; sender cannot provide<\/td><\/tr><tr><td>Severity<\/td><td>Temporary (requires configuration fix)<\/td><\/tr><tr><td>Common causes<\/td><td>TLS disabled, wrong port, outdated software, certificate issues<\/td><\/tr><tr><td>Fix approach<\/td><td>Enable TLS \u2192 verify port\/settings \u2192 update software \u2192 check certificates<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">What does TLS not available mean?<\/h2>\n\n\n\n<p>The receiving server demanded an encrypted transmission, but your sending infrastructure couldn&#8217;t establish TLS:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>TLS might be disabled on your side<\/li>\n\n\n\n<li>Negotiation failed during the handshake<\/li>\n\n\n\n<li>Certificate problems prevented a secure connection<\/li>\n\n\n\n<li>Protocol version mismatch (server requires newer TLS than you support)<\/li>\n<\/ul>\n\n\n\n<p>TLS in email transmission looks like:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Connection Type<\/td><td>Port<\/td><td>Encryption<\/td><\/tr><tr><td>STARTTLS<\/td><td>587<\/td><td>Starts plain, upgrades to TLS<\/td><\/tr><tr><td>Implicit TLS\/SSL<\/td><td>465<\/td><td>TLS from connection start<\/td><\/tr><tr><td>Unencrypted<\/td><td>25<\/td><td>No encryption (increasingly rejected)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Modern email infrastructure expects encrypted connections. Servers that accept only plain connections face delivery problems across most providers.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why does the 454 4.7.0 error occur?<\/h2>\n\n\n\n<p>TLS failures stem from configuration mismatches between sending and receiving infrastructure.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">TLS disabled in client<\/h3>\n\n\n\n<p>Email client settings don&#8217;t enable encryption:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Using the wrong port for the encryption type<\/li>\n\n\n\n<li>Security option set to &#8220;None&#8221; instead of TLS\/SSL<\/li>\n\n\n\n<li>Connection mode doesn&#8217;t match server requirements<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Wrong port configuration<\/h3>\n\n\n\n<p>Port and encryption type must align:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Port<\/td><td>Expected Mode<\/td><td>Mismatch Result<\/td><\/tr><tr><td>587<\/td><td>STARTTLS<\/td><td>Fails if using implicit SSL<\/td><\/tr><tr><td>465<\/td><td>Implicit SSL<\/td><td>Fails if expecting STARTTLS<\/td><\/tr><tr><td>25<\/td><td>Often unencrypted<\/td><td>Rejected by TLS-requiring servers<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Outdated software<\/h3>\n\n\n\n<p>Older email clients may not support modern TLS:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>TLS 1.0 and 1.1 are deprecated<\/li>\n\n\n\n<li>Many servers require TLS 1.2 minimum<\/li>\n\n\n\n<li>Ancient software can&#8217;t negotiate current protocols<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Certificate issues<\/h3>\n\n\n\n<p>Server-side certificate problems prevent TLS:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Expired certificate<\/li>\n\n\n\n<li>Hostname mismatch<\/li>\n\n\n\n<li>Incomplete certificate chain<\/li>\n\n\n\n<li>Self-signed certificate (not trusted)<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Firewall interference<\/h3>\n\n\n\n<p>Security appliances sometimes block TLS negotiation:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Blocked ports for encrypted traffic<\/li>\n\n\n\n<li>SMTP inspection corrupting TLS setup<\/li>\n\n\n\n<li>Deep packet inspection breaking handshake<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">How do you fix 454 4.7.0?<\/h2>\n\n\n\n<p>Configuration changes at the client or server level resolve TLS failures.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Email client fixes<\/h3>\n\n\n\n<p>Verify settings match provider requirements:<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Gmail<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Server: smtp.gmail.com<\/li>\n\n\n\n<li>Port: 587 (STARTTLS) or 465 (SSL)<\/li>\n\n\n\n<li>Encryption: TLS\/SSL enabled<\/li>\n\n\n\n<li>Authentication: Required (use app password if 2FA enabled)<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Outlook\/Microsoft 365<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Server: smtp.office365.com<\/li>\n\n\n\n<li>Port: 587<\/li>\n\n\n\n<li>Encryption: STARTTLS<\/li>\n\n\n\n<li>Authentication: Required<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Yahoo<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Server: smtp.mail.yahoo.com<\/li>\n\n\n\n<li>Port: 465 (SSL) or 587 (TLS)<\/li>\n\n\n\n<li>Encryption: SSL\/TLS enabled<\/li>\n\n\n\n<li>Authentication: Required (use app password)<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">General settings checklist<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Enable &#8220;outgoing server requires authentication&#8221;<\/li>\n\n\n\n<li>Select TLS or SSL (not &#8220;None&#8221;)<\/li>\n\n\n\n<li>Use correct port for encryption type<\/li>\n\n\n\n<li>Verify username and password accuracy<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Enable app passwords<\/h3>\n\n\n\n<p>Two-factor authentication requires app-specific passwords:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Regular password won&#8217;t work with 2FA enabled<\/li>\n\n\n\n<li>Generate app password in account security settings<\/li>\n\n\n\n<li>Use app password in email client configuration<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Update software<\/h3>\n\n\n\n<p>Older clients may lack TLS 1.2 support:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Update email client to current version<\/li>\n\n\n\n<li>Update operating system (TLS libraries)<\/li>\n\n\n\n<li>Consider switching to modern client if updates unavailable<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Server administrator fixes<\/h3>\n\n\n\n<p>For organizations managing mail infrastructure:<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Enable opportunistic TLS<\/h4>\n\n\n\n<p>Configure outbound TLS for all connections:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Attempt TLS encryption for every delivery<\/li>\n\n\n\n<li>Fall back gracefully if recipient doesn&#8217;t support<\/li>\n\n\n\n<li>Log TLS negotiation results for monitoring<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Verify certificates<\/h4>\n\n\n\n<p>Ensure valid SSL\/TLS certificates:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Certificate not expired<\/li>\n\n\n\n<li>Issued by trusted Certificate Authority<\/li>\n\n\n\n<li>Hostname matches server identity<\/li>\n\n\n\n<li>Complete certificate chain installed<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Check firewall rules<\/h4>\n\n\n\n<p>Verify encryption traffic isn&#8217;t blocked:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Port 587 and 465 open outbound<\/li>\n\n\n\n<li>SMTP inspection not corrupting TLS handshake<\/li>\n\n\n\n<li>No protocol-specific blocking on encrypted connections<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Synchronize clocks<\/h4>\n\n\n\n<p>Time mismatches cause authentication failures:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Server clocks within 5 minutes of accurate time<\/li>\n\n\n\n<li>NTP synchronization enabled<\/li>\n\n\n\n<li>Domain controllers synchronized (for Windows environments)<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">How do you prevent TLS failures?<\/h2>\n\n\n\n<p>Maintaining current infrastructure prevents encryption-related errors.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Keep software updated<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Update email clients regularly<\/li>\n\n\n\n<li>Patch server operating systems<\/li>\n\n\n\n<li>Monitor for TLS deprecation announcements<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Monitor certificate expiration<\/h3>\n\n\n\n<p>Set reminders before certificates expire:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Renew 30 days in advance<\/li>\n\n\n\n<li>Automate renewal where possible (Let&#8217;s Encrypt)<\/li>\n\n\n\n<li>Test after renewal<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Test after changes<\/h3>\n\n\n\n<p>Verify TLS works whenever infrastructure changes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Send test messages<\/li>\n\n\n\n<li>Check connection logs<\/li>\n\n\n\n<li>Verify handshake completion<\/li>\n<\/ul>\n\n\n\n\n<!-- EmailWarmup \u2014 Email Errors Campaign CTA Section -->\n<section id=\"ew-email-errors-consult\" aria-label=\"Help fixing email errors\">\n  <style>\n    \/* Scoped, theme-safe resets *\/\n    #ew-email-errors-consult, #ew-email-errors-consult *{\n      box-sizing:border-box;\n      -webkit-hyphens:none!important; -ms-hyphens:none!important; hyphens:none!important;\n      word-break:normal!important; overflow-wrap:anywhere;\n      font-family:system-ui,-apple-system,Segoe UI,Inter,Roboto,Arial,sans-serif!important;\n      color:#0f1115;\n    }\n\n    \/* Section wrapper *\/\n    #ew-email-errors-consult{\n      --radius:16px; --gap:14px;\n      --ink:#0f1115; --muted:#475569;\n      --border:#e5e7eb; --surface:#ffffff;\n\n      --tile1:#e9f0ff;\n      --tile2:#ecffd7;\n      --tile3:#efeaff;\n      --tile4:#ffe9f1;\n\n      background:\n        radial-gradient(1400px 600px at 10% -10%, #eef2ff 0%, 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(max-width:640px){\n      #ew-email-errors-consult .title{ font-size:24px; }\n    }\n  <\/style>\n\n  <div class=\"intro\">\n    <div class=\"eyebrow\">Need help fixing an email error?<\/div>\n    <h2 class=\"title\">Still stuck after trying the fix?<\/h2>\n    <p class=\"subtitle\">\n      Some email errors are easy to clear. Others point to deeper deliverability issues involving authentication, sender reputation, blacklisting, routing, or mailbox provider policy. If you would rather have an expert review it, speak with an\n      <a href=\"https:\/\/emailwarmup.com\/email-deliverability-consultant\">email delieverability consultant<\/a>\n      for free and we can help diagnose the issue and fix it on your behalf.\n    <\/p>\n  <\/div>\n\n  <div class=\"tiles\" role=\"list\">\n    <article class=\"tile t1\" role=\"listitem\">\n      <div class=\"icon\" aria-hidden=\"true\">\n        <svg width=\"18\" height=\"18\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\">\n          <path d=\"M21 15a2 2 0 0 1-2 2H7l-4 4V5a2 2 0 0 1 2-2h14a2 2 0 0 1 2 2z\"><\/path>\n        <\/svg>\n      <\/div>\n      <div>\n        <span class=\"h3like\">Root cause analysis<\/span>\n        <p>We look beyond the error message itself to find what is actually breaking delivery, trust, or inbox placement.<\/p>\n      <\/div>\n    <\/article>\n\n    <article class=\"tile t2\" role=\"listitem\">\n      <div class=\"icon\" aria-hidden=\"true\">\n        <svg width=\"18\" height=\"18\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\">\n          <path d=\"M20 6L9 17l-5-5\"><\/path>\n        <\/svg>\n      <\/div>\n      <div>\n        <span class=\"h3like\">Technical fixes handled for you<\/span>\n        <p>From SPF, DKIM, and DMARC to blacklist cleanup, DNS alignment, and sending setup, we can guide or implement the fix.<\/p>\n      <\/div>\n    <\/article>\n\n    <article class=\"tile t3\" role=\"listitem\">\n      <div class=\"icon\" aria-hidden=\"true\">\n        <svg width=\"18\" height=\"18\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\">\n          <path d=\"M12 20V10\"><\/path>\n          <path d=\"M18 20V4\"><\/path>\n          <path d=\"M6 20v-4\"><\/path>\n        <\/svg>\n      <\/div>\n      <div>\n        <span class=\"h3like\">Deliverability-first review<\/span>\n        <p>We assess whether the error is part of a bigger pattern hurting opens, replies, and overall campaign performance.<\/p>\n      <\/div>\n    <\/article>\n\n    <article class=\"tile t4\" role=\"listitem\">\n      <div class=\"icon\" aria-hidden=\"true\">\n        <svg width=\"18\" height=\"18\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\">\n          <path d=\"M12 12c2.8 0 5-2.2 5-5s-2.2-5-5-5-5 2.2-5 5 2.2 5 5 5z\"><\/path>\n          <path d=\"M2 22c1.5-4 5.5-6 10-6s8.5 2 10 6\"><\/path>\n        <\/svg>\n      <\/div>\n      <div>\n        <span class=\"h3like\">Free expert consultation<\/span>\n        <p>Talk to a real deliverability expert, get honest guidance, and see the next best step without pressure or upsells.<\/p>\n      <\/div>\n    <\/article>\n  <\/div>\n\n  <div class=\"bottom\">\n    <p>\n      <strong>When should you book a consultation?<\/strong> If the error keeps coming back, affects multiple mailboxes or domains, started after an ESP or DNS change, or is tied to spam placement, low inboxing, high bounce rates, or authentication failures, it is usually faster to get an expert involved early.\n    <\/p>\n  <\/div>\n\n  <div class=\"cta\">\n    <a class=\"btn\" href=\"https:\/\/emailwarmup.com\/email-deliverability-consultant\" target=\"_blank\" rel=\"noopener\">\n      Talk to a deliverability expert for free\n      <svg width=\"18\" height=\"18\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" aria-hidden=\"true\">\n        <path d=\"M5 12h14\"><\/path>\n        <path d=\"M12 5l7 7-7 7\"><\/path>\n      <\/svg>\n    <\/a>\n  <\/div>\n<\/section>\n\n\n\n\n\n<h2 class=\"wp-block-heading\">Frequently asked questions<\/h2>\n\n\n\n<p>Here are some commonly asked questions about this error:<\/p>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1773284557202\"><strong class=\"schema-faq-question\">Can I just disable TLS requirement?<\/strong> <p class=\"schema-faq-answer\">On your own server, yes (though not recommended). On recipient servers, no \u2014 you cannot force them to accept unencrypted connections. Modern email security expects encryption; disabling TLS invites interception and damages <a href=\"https:\/\/emailwarmup.com\/blog\/email-deliverability\/what-is-email-deliverability\/\">deliverability<\/a>.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1773284565325\"><strong class=\"schema-faq-question\">Why does TLS work for some recipients but not others?<\/strong> <p class=\"schema-faq-answer\">Different servers have different requirements. Some accept unencrypted connections (legacy behavior), while others require TLS (modern security). If TLS fails only for specific recipients, the issue might be their configuration or certificate problems on their end.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1773284570897\"><strong class=\"schema-faq-question\">Does TLS affect email content?<\/strong> <p class=\"schema-faq-answer\">TLS encrypts transmission (between servers), not storage. Email content isn&#8217;t encrypted end-to-end by TLS \u2014 it&#8217;s protected only during transit. For content encryption, use S\/MIME or PGP (separate from TLS transport encryption).<\/p> <\/div> <\/div>\n","protected":false},"excerpt":{"rendered":"<p>The 454 4.7.0 error means the recipient&#8217;s server requires TLS encryption, but your sending server cannot establish a secure connection \u2014 either TLS isn&#8217;t enabled, negotiation failed, or certificate problems blocked the handshake.&nbsp; Fix it by enabling TLS\/SSL in your email client settings (use port 587 with STARTTLS or port 465 with implicit SSL), verifying [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":5283,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","footnotes":""},"categories":[38],"tags":[],"class_list":["post-5282","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-email-errors"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>How To Fix 454 4.7.0 | TLS Not Available (Encryption Required)<\/title>\n<meta name=\"description\" content=\"The 454 4.7.0 error means recipient&#039;s server requires TLS encryption, but your sending server can&#039;t establish a secure connection. Let&#039;s fix!\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How To Fix 454 4.7.0 | TLS Not Available (Encryption Required)\" \/>\n<meta property=\"og:description\" content=\"The 454 4.7.0 error means recipient&#039;s server requires TLS encryption, but your sending server can&#039;t establish a secure connection. 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Modern email security expects encryption; disabling TLS invites interception and damages <a href=\"https:\/\/emailwarmup.com\/blog\/email-deliverability\/what-is-email-deliverability\/\">deliverability<\/a>.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/#faq-question-1773284565325","position":2,"url":"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/#faq-question-1773284565325","name":"Why does TLS work for some recipients but not others?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Different servers have different requirements. Some accept unencrypted connections (legacy behavior), while others require TLS (modern security). If TLS fails only for specific recipients, the issue might be their configuration or certificate problems on their end.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/#faq-question-1773284570897","position":3,"url":"https:\/\/emailwarmup.com\/blog\/email-errors\/how-to-fix-454-4-7-0-tls-not-available\/#faq-question-1773284570897","name":"Does TLS affect email content?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"TLS encrypts transmission (between servers), not storage. Email content isn't encrypted end-to-end by TLS \u2014 it's protected only during transit. For content encryption, use S\/MIME or PGP (separate from TLS transport encryption).","inLanguage":"en-US"},"inLanguage":"en-US"}]}},"uagb_featured_image_src":{"full":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",3448,2195,false],"thumbnail":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",150,95,false],"medium":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",300,191,false],"medium_large":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",768,489,false],"large":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",1024,652,false],"1536x1536":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",1536,978,false],"2048x2048":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",2048,1304,false],"profile_24":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",24,15,false],"profile_48":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",48,31,false],"profile_96":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",96,61,false],"profile_150":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",150,95,false],"profile_300":["https:\/\/emailwarmup.com\/blog\/wp-content\/uploads\/2026\/03\/454-4.7.0_11zon.jpg",300,191,false]},"uagb_author_info":{"display_name":"Daniyal Dehleh","author_link":"https:\/\/emailwarmup.com\/blog\/author\/daniyaldehleh\/"},"uagb_comment_info":0,"uagb_excerpt":"The 454 4.7.0 error means the recipient&#8217;s server requires TLS encryption, but your sending server cannot establish a secure connection \u2014 either TLS isn&#8217;t enabled, negotiation failed, or certificate problems blocked the handshake.&nbsp; Fix it by enabling TLS\/SSL in your email client settings (use port 587 with STARTTLS or port 465 with implicit SSL), verifying&hellip;","_links":{"self":[{"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/posts\/5282","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/comments?post=5282"}],"version-history":[{"count":1,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/posts\/5282\/revisions"}],"predecessor-version":[{"id":5284,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/posts\/5282\/revisions\/5284"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/media\/5283"}],"wp:attachment":[{"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/media?parent=5282"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/categories?post=5282"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/emailwarmup.com\/blog\/wp-json\/wp\/v2\/tags?post=5282"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}