Microsoft 365 Error Codes

How to Fix Office 365 Error 550 Domain Is Not Hosted Here

Jason Miller Oct 26, 2026 870 views

Question details

External senders are receiving a 550 bounce message when trying to send emails to a custom domain hosted on Office 365.

How to Fix Office 365 Error 550: Domain Is Not Hosted Here

Product: Microsoft Office 365
Device & OS: not provided
Scenario: Receiving external emails after configuring a custom domain in Microsoft 365.
Observed behavior: External senders receive an Error 550 bounce message stating the domain is not hosted here, while internal emails deliver successfully.

Before you start

Ensure you have administrative access to your DNS hosting provider's control panel and your Microsoft 365 Admin Center to verify and update DNS records.

Solution 1Recommended

Update MX Records and Wait for DNS Propagation

Correctly configure your domain's MX records to point to Microsoft 365 and remove any conflicting records from previous providers.

The most common cause of Error 550 is incorrect or conflicting MX records in your domain's DNS settings. Even if internal emails work, external mail servers rely on accurate MX records to locate your Microsoft 365 inbox.

Log in to your DNS host

Access the administrative portal of your DNS hosting provider (e.g., GoDaddy, Cloudflare, Namecheap) and navigate to the DNS management or zone editor page.

Remove conflicting MX records

Locate your current MX records and delete any legacy records that route mail to previous email providers or servers other than Office 365.

Add the correct Microsoft 365 MX record

Create a new MX record pointing to Microsoft 365. The value should look similar to <MX token>.mail.protection.outlook.com, which can be found in your Microsoft 365 Admin Center.

Save and wait for propagation

Save the changes to your DNS zone. Allow 24 to 72 hours for the new DNS settings to fully propagate across global mail servers.

Update MX Records and Wait for DNS Propagation

DNS Propagation Delay: While DNS changes typically process within 15 minutes on your host's end, full global propagation can take up to 72 hours. Internal emails may continue to work normally during this period, masking the external issue.

Solution 2

Verify Domain Configuration in Microsoft 365

Ensure Microsoft 365 recognizes your custom domain as properly set up and healthy to prevent internal routing issues.

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Frequently Asked Questions

Why do internal emails still work while external senders get Error 550?

Internal Microsoft 365 routing does not always rely on public DNS MX records. If your domain is registered within your tenant, internal users can successfully email each other even if your external MX records are pointing to the wrong hosting provider.

How do I find my exact MX record value for Microsoft 365?

You can find your specific MX record token by logging into the Microsoft 365 Admin Center, navigating to Settings > Domains, selecting your custom domain, and viewing the required DNS records page. The value typically ends in mail.protection.outlook.com.

What should I do if the Error 550 persists after 72 hours?

If external senders still receive the Error 550 bounce message after 72 hours of DNS propagation, double-check your DNS host for duplicate or conflicting MX records. If everything is correct, gather the detailed bounce-back message and contact Microsoft support for investigation.

Microsoft Office Error Codes