Outlook Error Codes

How to Fix Exchange Error 550 5.7.1 Recipient Address Rejected

Muhammad Talha Sep 28, 2026 869 views

Question details

The user is unable to deliver an email from a corporate account due to a delivery failure indicating the recipient address is marked as invalid.

Fix Exchange Error 550 5.7.1: Recipient Address Rejected

Product: Microsoft Exchange
Device & OS: not provided
Scenario: Sending an email from a corporate Exchange or Outlook account to a specific recipient.
Observed behavior: The email bounces back with a Non-Delivery Report (NDR) showing the message '550 5.7.1: Recipient address rejected: User email address is marked as invalid'.

Before you start

Double-check that you have typed the recipient's email address correctly, without any typos, extra spaces, or unsupported characters. If the address is correct and the issue persists, you will likely need assistance from your organization's IT department.

Solution 1Recommended

Verify Recipient Details and Contact Your IT Administrator

Since this error typically involves server-side policies or mailbox restrictions, validating the address and contacting your IT administrator is the most effective approach for standard users.

Error 550 5.7.1 is usually a server-side rejection, meaning your local Outlook client is functioning properly, but the server is blocking the message. This can happen if the recipient's mailbox is disabled, full, or restricted by organizational policies.

Verify the email address

Look closely at the 'To' field in your bounced email. Check the recipient's email address for any typos, missing letters, or incorrect domain names.

Confirm mailbox status via alternative methods

If possible, reach out to the recipient through a phone call or an instant messaging app to ensure their email account is still active and capable of receiving external messages.

Forward the NDR to IT Support

Save or screenshot the exact Non-Delivery Report (NDR) containing the '550 5.7.1' error code and send it to your company's IT helpdesk. They will need this specific code to investigate the server logs.

Verify Recipient Details and Contact Your IT Administrator

Provide complete error details: When contacting IT, always include the full bounce-back message. The hidden diagnostic headers in the NDR help administrators pinpoint exactly which server rejected the message.

Solution 2

Troubleshoot Mail-Flow Policies and Connectors (For IT Admins)

Exchange Administrators should check mail-flow rules, connectors, and blocklists to resolve the delivery failure between organizations.

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Frequently Asked Questions

What does error code 550 5.7.1 mean in Microsoft Exchange?

This error typically indicates a delivery authorization or policy issue. It means the recipient's email server actively rejected the message, often due to security policies, incorrect email address routing, spam filter blocks, or server misconfigurations.

Can I fix the 550 5.7.1 error myself as an end user?

Generally, no. Aside from verifying that you typed the recipient's email address perfectly, fixing this error requires an IT administrator. They need to check mail-flow rules, directory syncing, spam filters, or connector settings in the Exchange Admin Center.

Why is an internal company email bouncing back with this error?

If an internal email bounces with this error, the recipient's mailbox might be disabled, hidden from the Global Address List, or there could be a misconfigured routing rule within your organization's own Exchange server.

How do IT admins trace the 550 5.7.1 error in Microsoft 365?

Administrators can log into the Exchange Admin Center, navigate to the 'Mail flow' menu, and use the 'Message trace' tool. By entering the sender and recipient details for the failed email, the trace logs will reveal the exact policy or rule that blocked the message.

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