Error code 550 5.7.x in Microsoft Exchange

Issue symptoms

End users receive a bounce-back notification from Microsoft after they send an email to a support address

The notification starts with: Your message could not be delivered

The message includes an error or status code with 550 5.7.x

Another message might look like: 550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555).

The emails don't reach Zendesk

The text of the message will be different for each underlying issue. However, the main problem remains the same: the user's email was rejected before it could reach Zendesk.

Root cause

Typically, these errors are linked to the fact that:

Your organization may not allow external forwarding in Microsoft

Additional settings in Microsoft Exchange prevent you from automatically forwarding emails

Microsoft may have updated its policies around automatic email forwarding, and it may affect support addresses that synced in the past. This type of error can occur on a support address that previously worked. That typically means something has changed. For example, if Microsoft implements a new policy for email forwarding, previous addresses may not meet the new requirements without an update. For more information, see Forwarding incoming email from your existing email address to Zendesk Support.

Disclaimer: These errors are generated by Microsoft, not Zendesk. Zendesk cannot assist in resolving these errors. Rules or spam policies of Microsoft 365 may affect external forwarding. If the resolution steps don't seem to apply to you, or if the issue continues after you change your outbound spam protection settings, contact Microsoft Support for help.

Resolution steps

If your users suddenly report bounce-back notifications and error messages, contact the Microsoft administrator in your company

Your administrator needs to review the error message and correct your email configuration accordingly outside of Zendesk with the guidance below

Ask your administrator to verify your outbound spam filter policy > Set your Automatic forwarding to On, instead of Automatic - System-controlled

Configure your remote domain settings to allow automatic email forwarding to some or all external domains. Don't disable auto-forwarding on your default remote domain, as when users try to auto-forward an email to another domain, they can change their settings or create the inbox rule, but their messages will not be transmitted.

Ensure your administrator didn't set up any conditions and actions in Exchange mail flow rules, also known as transport rules, to detect and block automatically forwarded messages to external recipients

When your administrator corrects the settings in Microsoft Exchange, ask your Zendesk admin to access Zendesk > Admin Center > Channels > Voice and email > Email > Manage support addresses > Click the options menu icon next to your Microsoft email address, select Verify forwarding > Ensure that no error appears

Alternatively, connect your non-Zendesk email servers, based on Microsoft Exchange, to your Zendesk account with the latest Microsoft Exchange connector

For more information, see:

Control automatic external email forwarding in Microsoft 365

Connecting your Microsoft Exchange account to Zendesk