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Fix Microsoft Email Messages Delayed or Rejected by BigPond
Question details
Emails sent from Telstra or BigPond addresses to Microsoft 365 and Outlook recipients are experiencing delivery delays or being completely rejected.
- Product
- Microsoft 365 and BigPond
- Device & OS
- not provided
- Scenario
- A user attempts to send an email from a BigPond or Telstra account to a recipient using Microsoft email services.
- Observed behavior
- The message is either significantly delayed or triggers a Non-Delivery Report (NDR) due to sender-score filtering or IP reputation blocks on Microsoft's cloud email systems.
Before contacting support, locate the Non-Delivery Report (NDR) bounce-back email in your BigPond inbox and ensure you have copied the original message headers and error codes.
Report IP Reputation Issues to Telstra / BigPond Support
Since the sending mailbox and outbound relay servers belong to Telstra, they must investigate and resolve the IP reputation flags causing Microsoft to block the emails.
When Microsoft 365 rejects an email from an external domain like BigPond, it is typically because the sending server's IP address has been flagged for spam or has a poor sender reputation. Because this outbound server is outside of Microsoft's control, Telstra needs to intervene and request delisting.
Open the bounce-back email you received. Note the exact timestamp, your sender address, and the recipient's Microsoft 365 address.
Look for the 'Diagnostic information for administrators' section within the NDR and copy the full text, including the original message headers.
Reach out to Telstra or BigPond customer support and provide them with the NDR details. Ask them to investigate their outbound IP reputation and sender-score filtering.
Provide Headers to Microsoft 365 IT Administrators
If you are the intended recipient using Microsoft 365, your IT administrator can trace the blocked message and submit it for analysis to prevent future false positives.
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Frequently Asked Questions
Why are my BigPond emails suddenly bouncing back from Microsoft 365?
This usually happens when the IP address of BigPond's outgoing email server is temporarily flagged by Microsoft's automated anti-spam filters due to a drop in sender-score or a compromised account on the same server.
Can I fix this BigPond rejection issue by modifying my Outlook settings?
No, this is a server-to-server routing issue. Adjusting your personal Outlook client settings will not bypass Microsoft's enterprise-level cloud anti-spam filters.
What is an NDR and why do I need it?
An NDR (Non-Delivery Report) is the automated bounce-back message you receive when an email fails to deliver. It contains specific error codes (like 5.7.1 or 5.1.0) and routing headers that support teams need to identify exactly why the message was blocked.
