If a user is receiving a 550 5.7.520 email bounce relating to External Forwarding. The problem is likely related to the default Microsoft Office 365 Exchange Online Exchange Online Protection Anti Spam filters.
Delivery has failed to these recipients or groups: <User> (<user email>)
Your message wasn’t delivered because the recipient’s email provider rejected it.
Diagnostic information for administrators:
Generating server: CO1PR13MB4949.namprd13.prod.outlook.com
Remote Server returned ‘550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555)’
The solution is to:
- Surf to security.microsoft.com
- Expand POLICIES & RULES
- Click THREAT POLICIES
- Click ANTI-SPAM
- Click ANTI-SPAM OUTBOUND POLICY (DEFAULT)
- Click EDIT PROTECTION SETTINGS
- Change FORWARDING RULES > AUTOMATIC FORWARDING RULES to ON – FORWARDING IS ENABLED
However, there are very good reasons to have this setting set to OFF-FORWARDING IS DISABLED and we explain why in the video above.