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smtp-errors/codes/421-4-3-2.html
2026-01-22 21:25:23 +00:00

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<title>421 4.3.2 — Service not available (system problem)</title>
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<span class="code">421 4.3.2</span>
<span class="badge b-temp">Temporary</span>
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<h1>Service not available (system problem)</h1>
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The receiving mail system was temporarily unable to accept the message due to a short-lived system issue.
This is usually not caused by the person sending the email.
</p>
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<a class="btn primary" href="../what-to-do/421-4-3-2.html">Open “What to do”</a>
<a class="btn" href="../index.html">Pick another code</a>
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<img src="../assets/img/placeholder.png" alt="Placeholder illustration for 421 4.3.2" />
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Image slot: upload a simple “temporary issue / retry later” visual and replace <code>placeholder.png</code>.
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<h3>Quick next step</h3>
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<li><b>Wait and retry.</b> Most systems retry automatically.</li>
<li>If it continues beyond a reasonable window, contact support with the bounce details.</li>
</ul>
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<div class="section-title">What it usually means</div>
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<h2>Plain-English meaning</h2>
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The destination email system is having trouble right now (maintenance, overload, or a temporary internal problem),
so it asked the sender to try again later.
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<h2>Is this a “hard failure”?</h2>
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No. <b>421 4.3.2 is temporary</b>. Many systems will retry automatically and succeed once the destination recovers.
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<div class="section-title">Common causes (non-technical)</div>
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<ul>
<li>The recipients email provider is having a short service issue.</li>
<li>The destination system is busy (high volume) and is slowing intake briefly.</li>
<li>Routine maintenance or a transient internal error.</li>
</ul>
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<div class="section-title">Who needs to act?</div>
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<h2>Sender</h2>
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Usually nothing—just allow the system to retry. If you must send immediately, you can try again later or
use an alternate channel temporarily.
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<h2>Recipient / IT</h2>
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If this happens repeatedly, support may need to check the mail service health and confirm there isnt a broader outage.
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<div class="section-title">What to send support (if it persists)</div>
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<p>If the problem lasts longer than expected, include:</p>
<ul>
<li>The full bounce/error text (or screenshot)</li>
<li>Sender address + recipient address</li>
<li>Date/time (and timezone)</li>
<li>Whether its happening to one recipient or many</li>
</ul>
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<div class="section-title">Mini-FAQ</div>
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<h2>Should we resend right away?</h2>
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You can, but its usually better to wait a bit. Most mail systems retry automatically and succeed once the destination recovers.
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<h2>Is this a spam block?</h2>
<p>
Usually no. This code most often indicates a temporary service condition on the receiving side, not a reputation block.
</p>
</article>
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<span>421 4.3.2 is listed as a temporary service/system problem in your source reference.</span>
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