I am experiencing an issue where emails sent to recipients outside Microsoft are not being delivered. - My objective is to have these external emails successfully delivered.

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I am experiencing an issue where emails sent to recipients outside Microsoft are not being delivered. - My objective is to have these external emails successfully delivered.

Vivek Ranjan 20 Microsoft Employee

The outbound email is not failing within Power Automate itself. The Office 365 Outlook "Send an email" action submits the message successfully, but Exchange Online rejects it at the transport layer and returns the non-delivery report: "550 5.7.1 TRANSPORT.RULES.RejectMessage; the message was rejected by organization policy." This response is produced by a custom Exchange Online mail flow rule (transport rule) in the tenant that is configured to reject messages matching its conditions - in this case, messages sent to recipients outside the organization. The enhanced status code 5.7.1 is the default DSN returned by the mail flow rule "Reject the message" action. This is an intentional organizational email policy - not a Power Automate platform, connector, licensing, or throttling defect. The flow and the Office 365 Outlook connector are working as designed; the rejection happens entirely in Exchange Online after the message is handed off. Why external delivery is blocked: The message matched the conditions of a mail flow rule that blocks external recipients, so Exchange Online refused delivery and returned the message to the sender with the 5.7.1 NDR. Because this is enforced by an Exchange Online transport rule, the behavior can only be changed by an Exchange Online administrator in the tenant; it cannot be resolved or worked around from within Power Automate. Resolution / next steps (to be performed by an Exchange Online administrator in the tenant): 1. In the Exchange admin center, go to Mail flow > Rules and identify the rule whose action is "Reject the message" returning enhanced status code 5.7.1 / TRANSPORT.RULES.RejectMessage. 2. Run a message trace for the rejected message to confirm exactly which transport rule matched. 3. Modify the identified rule to permit the required flow - add an exception for the sending account or for the messages generated by the flow, or adjust the rule's conditions/scope so the legitimate external messages are allowed. Alternatively, if the block is intended by policy, the message content or recipients must be changed so they no longer match the rule's conditions. Reference documentation: - Fix NDR error 550 5.7.1 in Exchange Online: [Moderator note: Personally Identifiable Information removed]

URL: https://learn.microsoft.com/troubleshoot/exchange/email-delivery/ndr/fix-error-code-550-5-7-1-in-exchange-online. Click or tap if you trust this link.") - Mail flow rule actions in Exchange Online: [Moderator note: Personally Identifiable Information removed]

URL: https://learn.microsoft.com/exchange/security-and-compliance/mail-flow-rules/mail-flow-rule-actions. Click or tap if you trust this link.") - Troubleshoot flow run failures: [Moderator note: Personally Identifiable Information removed]

URL: https://learn.microsoft.com/power-automate/fix-flow-failures. Click or tap if you trust this link.")

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Answer 1

Good day Vivek, and I appreciate the clear explanation of your concern.

Based on the non-delivery report showing “550 5.7.1 TRANSPORT.RULES.RejectMessage; the message was rejected by organization policy”, the email is being blocked by a policy configured in Exchange Online by your organization's IT admin.

To move forward, I recommend contact your organization's IT administrator and ask them to:

Note: In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support

Review the mail flow rules configured in Exchange admin center.

Run a message trace for the affected email to identify which rule caused the rejection.

Update the rule or add an exception if the external recipients should be allowed.

Since the restriction is enforced by your organization's Exchange Online policy, only an administrator with the appropriate permissions can review and modify the configuration. As a forum user, I don't have the permissions or tools needed to modify your organization's configuration.

I hope this helps clarify the cause of the issue. If you have any questions or need further support, please don’t hesitate to reach out at any time.

Thank you for your patience and understanding.

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