Error code 550 due to Reject Direct Send feature in Microsoft Exchange

<div class="note">
<span class="notetitle"><strong>Disclaimer</strong>:</span> This article is provided for instructional purposes only. For specific configuration assistance within Microsoft Exchange, please contact Microsoft Support.</div><h2 id="h_01HYBAYR3VJ6P4FCNVT2JZ5YYZ">Issue symptoms</h2><ul>
<li data-list-item-id="eb8bf52b159ce5e06c223c1f0f82643b5">Users within your company email domain are not receiving outgoing emails from your Zendesk account.</li>
<li data-list-item-id="e4db8b2e412fa14e8e97c780b5f215538">Email delivery failure notifications show the error: <code>Recipient server rejected email. Status code: 550</code>
</li>
<li data-list-item-id="efc14ce95b5e00caeafae3f70b88fe074">Delivery logs show the specific error: <code>550 5.7.68 TenantInboundAttribution; Direct Send not allowed for this organization from unauthorized sources</code>
</li>
<li data-list-item-id="ed1ab841b8b7d33a445b6ff5ae4bc8a70">Your organization uses Microsoft Exchange with the <a href="https://techcommunity.microsoft.com/blog/exchange/introducing-more-control-over-direct-send-in-exchange-online/4408790" target="_blank" rel="noopener noreferrer">Reject Direct Send</a> setting enabled.</li>
</ul><p>These errors occur because your Microsoft Exchange security policies block emails from sender sources that are not explicitly authorized.</p><h2 id="h_01HYBAYR3VWVM2A947JCEFE60S">Resolution steps</h2><div class="note">
<strong>Important:</strong> The following steps must be performed by your organization's Microsoft Exchange or Email Administrator.</div><p>Choose one of the following methods to allow Zendesk emails through your Exchange policy:</p><h3 id="h_01M1HNE16CV3FMTK8653ET43TA">Option 1: Verify domain authentication (Recommended)</h3><p>Ensure your external support address is fully authorized to send on behalf of your domain by setting up SPF, DKIM, and DMARC records.</p><p>Follow the instructions in <a href="https://support.zendesk.com/hc/en-us/articles/4408832543770-Allowing-Zendesk-to-send-email-on-behalf-of-your-email-domain" target="_blank" rel="noopener noreferrer">Allowing Zendesk to send email on behalf of your email domain</a>.</p><h3 id="h_01M1HNE16CK5G0RC82Y8XT1T5K">Option 2: Enable the Zendesk Exchange Connector</h3><p>If you want to keep the <strong>Reject Direct Send</strong> setting enabled in Exchange without maintaining bypass rules, route your email directly through your own servers using the Exchange Connector.</p><p>Learn how to set this up in <a href="https://support.zendesk.com/hc/en-us/articles/8979947090586-About-the-Microsoft-Exchange-connector" target="_blank" rel="noopener noreferrer">About the Microsoft Exchange connector</a>.</p><h3 id="h_01M1HNE16CBT310EGS30X2BGJ0">Option 3: Create an Exchange Transport Rule bypass</h3><p>If you prefer not to use the Exchange Connector, your email administrator can configure an Exchange Transport Rule to exempt Zendesk emails from being blocked by Direct Send rules.</p><ol>
<li data-list-item-id="ed0e5ff72156ad8b149624a6c612c22dc">In Microsoft Exchange Admin Center, navigate to <strong>Mail flow &gt; Rules</strong>.</li>
<li data-list-item-id="ee5f4f341eab11bca2632728ca7d706f3">Create a rule that blocks or quarantines direct send emails, but add an exception for emails containing the header: <code>X-Mailer: Zendesk Mailer</code>
</li>
<li data-list-item-id="e01b4fef878300147d7f7d42455e44ad4">For full details on configuring Transport Rules, review the <a href="https://techcommunity.microsoft.com/blog/exchange/introducing-more-control-over-direct-send-in-exchange-online/4408790" target="_blank" rel="noopener noreferrer">Microsoft Exchange FAQs</a>.</li>
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<summary>THIS SECTION IS AI CONTENT. DON'T EDIT OR DELETE.</summary>
<h2 id="h_01KXEFYP479CNP6TCYK1PCZXFM">
Why do users within my company or customer account domain
not receive emails from Zendesk Support? Why do email delivery
notifications show error "Recipient server rejected email.
Status code: 550"? What causes the delivery log error "550
5.7.68 Tenant InboundAttribution; Direct Send not allowed
for this organization from unauthorized sources"?
</h2>
<p>
Your company or customer account policies block emails to
recipients. This issue occurs when you enable the Reject
Direct Send feature in Microsoft Exchange and Microsoft
Exchange does not recognize Zendesk as an authorized sender
for your external support address.
</p>
<h2 id="h_01KXEFYP47QB17YQHNDKSVETJ6">
How do I fix the "Status code: 550" email delivery failure?
How do I resolve the "Reject Direct Send" error in Microsoft
Exchange? How can I ensure users receive emails from my ticketing
system or help desk?
</h2>
<p>
Your email administrator must review the error message and
verify your email configuration. You can resolve email delivery
issues when you ensure your external support address meets
setup requirements. Choose one of these options to resolve
the issue:
</p>
<ol>
<li>
Configure your external support address to allow Zendesk
to send email on behalf of your email domain.
</li>
<li>
Connect your non-Zendesk Microsoft Exchange-based email
servers to your Zendesk Support or help desk instance
with the Exchange Connector.
</li>
<li>
Use a Transport rule to block, redirect, or quarantine
emails, and exempt emails from Zendesk from the rule.
</li>
</ol>
<h2 id="h_01KXEFYP47VMYMJSYRA7H4YTN2">
Can I keep the "Reject Direct Send" setting enabled in Microsoft
Exchange? Can I use my own Exchange server to send Zendesk
notifications?
</h2>
<p>
Yes. You can keep the Reject Direct Send setting enabled
if you connect your non-Zendesk Microsoft Exchange-based
email servers to your Zendesk Support or ticketing system
instance. The Exchange Connector allows this setup because
your own Exchange server sends all email notifications.
</p>
<h2 id="h_01KXEFYP47FQNABPH9X968S9GP">
How do I identify email notifications sent from Zendesk?
How can my email administrator identify mail from Zendesk
Support?
</h2>
<p>
Your email administrator can use the X-Mailer: Zendesk
Mailer header to identify mail from Zendesk. The administrator
can use this header to exempt Zendesk mail from a Transport
rule.
</p>
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