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Fix Microsoft 365 Email Delivery DNS Error 550 5.4.311
Question details
Users are unable to successfully send emails from Microsoft 365 due to intermittent DNS routing errors, even when emails from other providers successfully deliver.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Attempting to send an email from a Microsoft 365 account to a recipient whose domain was recently renewed or updated.
- Observed behavior
- The email fails to deliver and returns a bounce-back message citing DNS Error 550 5.4.311 and an InfoMxLoopback error.
Ensure you have the exact Non-Delivery Report (NDR) or bounce-back email on hand, as it contains the critical error codes required to isolate the routing issue.
Verify Recipient DNS Configuration and MX Records
Since the issue occurs after a domain renewal, the recipient's DNS data may be stale or incorrectly configured. Contacting their admin is the most direct fix.
A 550 5.4.311 error paired with an InfoMxLoopback usually points to a problem on the recipient's end, not the sender's. When a domain is renewed or transferred, MX (Mail Exchange) records can sometimes reset or become inconsistent across different global DNS servers.
Reach out to the recipient or their IT administrator using an alternative communication method, such as a phone call or a different email provider like Gmail.
Share the full bounce-back message you received from Microsoft 365, explicitly mentioning the 'Error 550 5.4.311' and 'InfoMxLoopback' codes.
Ask the administrator to check their domain registrar or DNS hosting provider to ensure their MX records are correctly pointing to their active mail server.
Create a Service Request in the Microsoft 365 Admin Center
If the recipient's DNS is verified as correct but emails still fail, Microsoft support engineers need to inspect the backend delivery path.
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Frequently Asked Questions
What does DNS Error 550 5.4.311 mean?
This error code indicates a routing issue where the sending mail server cannot find a valid delivery path to the recipient's domain. It is most commonly caused by a missing, incorrect, or stale MX (Mail Exchange) record in the recipient's DNS configuration.
Why do emails from Gmail deliver fine while Microsoft 365 fails?
Different email service providers rely on different DNS cache servers around the world. If a domain was recently renewed or updated, Gmail's servers might have received the new DNS records faster than Microsoft 365's servers, causing intermittent failures.
What is an InfoMxLoopback error?
An InfoMxLoopback error occurs when a mail server detects a routing loop. This happens when the MX records for a domain point to a server that refuses to accept the mail for that domain, bouncing it continuously until the loop is forcefully stopped by the system.
How long does a domain renewal take to affect email delivery?
While domain renewals are often processed quickly, the associated DNS propagation can take anywhere from 24 to 72 hours to update across all global servers. You may experience intermittent email delivery issues during this period.
