Why are my emails soft bouncing with Bigpond after implementing DMARC changes?

Key findings

• Content rejection: The error message '558 5.7.1 Message content rejected due to suspected spam. IB703' clearly indicates that the bounce is due to Bigpond's spam filters identifying something within the email's content as suspicious or spammy, not an authentication failure.
• DMARC policy impact: While DMARC changes might coincide with these bounces, they are unlikely to be the direct cause of a content-based rejection. Instead, tightening a DMARC policy (e.g., to p=quarantine or p=reject) ensures that all legitimate mail is properly authenticated, but it doesn't solve content issues. Learn more about safely transitioning DMARC policies.
• Bigpond sensitivity: Bigpond (and its parent company Telstra) is known for having strict spam filters and is highly sensitive to sender reputation, content, and sending patterns.
• High bounce rates: A 95.5% soft bounce rate specifically for Bigpond recipients, even with an engaged segment, points to a significant issue with how Bigpond is receiving and evaluating your email traffic.

Key considerations

• Content audit: Conduct a thorough review of your email content for elements that might trigger spam filters, such as excessive links, certain keywords, poor HTML, or image-to-text ratio. You might also be interested in why Bigpond emails bounce for content reasons.
• Sender reputation: Even with correct DMARC, SPF, and DKIM, your sender reputation with Bigpond might be low. This could be due to past sending practices, low engagement rates from Bigpond users, or being on an internal blocklist.
• Engagement segmentation: While sending to engaged segments is good, a 14-day engagement window might still be too broad for a sensitive ISP like Bigpond, especially if the engagement is not recent. Consider tightening this further or re-engaging less active subscribers with specific campaigns.
• Feedback loops: Monitor any available feedback loop data (if Bigpond provides it) to identify specific issues reported by users, such as spam complaints. This can help fix DMARC fail errors in a broader context of email health.
• IP and domain blocklists: Even if not the primary cause of a content-based rejection, ensure your sending IP and domain are not on any major blocklists (also known as blacklists). Being blocklisted can severely impact deliverability.

Key opinions

• Bigpond's strictness: Many marketers agree that Bigpond is particularly sensitive to sending practices and email content. This often means that even minor issues can lead to significant bounce rates, as seen in cases where Bigpond emails are bouncing.
• Content is king (and queen): A recurring theme is that the bounce reason 'Message content rejected due to suspected spam' points directly to issues within the email's creative or structure, rather than authentication.
• Volume sensitivity: Sending higher volumes, even to seemingly engaged segments, can exacerbate problems with sensitive ISPs. Gradual increases and consistent good sending practices are often recommended.
• Engaged segments matter: While sending to engaged users is a fundamental best practice, marketers note that the definition of 'engaged' might need to be much tighter for ISPs like Bigpond, sometimes even less than 14 days.

Key considerations

• Review email content rigorously: Pay close attention to subject lines, body text, links, and image content. Generic or overly promotional language can be a red flag. Marketers suggest testing different content variations.
• List segmentation and hygiene: Beyond engagement, ensure lists are regularly cleaned to remove inactive or problematic addresses. This helps avoid soft bounces and improves deliverability.
• Investigate sending reputation: Even if DMARC passes, a poor reputation with Bigpond specifically can cause issues. Check for any historical spam complaints or low engagement from Bigpond users on your domain. Understanding sender reputation management is crucial.
• Engage ISP postmasters: While direct support can be generic, some marketers have found success by reaching out to ISP postmaster teams with detailed logs and authentication passes.

Key opinions

• DMARC vs. Content Filtering: Experts clarify that DMARC primarily validates the sender's identity, preventing spoofing. It does not certify content quality. A content-based rejection means the message passed DMARC but failed Bigpond's separate content-scoring system. This distinction is critical for troubleshooting blocked emails.
• Reputation is paramount: ISPs like Bigpond weigh sender reputation heavily. Low engagement, high complaint rates, or previously bad sending habits can lead to stricter content filtering, even if the current content is benign. Learn how to recover domain reputation.
• Engagement signals: Positive engagement from subscribers at a given ISP builds trust. A sudden drop in engagement or a high bounce rate specifically for Bigpond suggests a disconnect that needs immediate attention.
• Hidden triggers: Some elements, like hidden text, specific URL shorteners, or even certain character sets, can silently trigger spam filters, leading to rejections without clear indication to the sender.

Key considerations

• Deep content analysis: Use internal and external tools to run a spam score check on your email content. Pay attention to both visible and invisible elements that could be problematic.
• Warm-up if necessary: If there's been a significant change in sending volume or a pause, a gradual warming-up process specifically for Bigpond might be needed to rebuild trust.
• Segment sensitive audiences: For ISPs like Bigpond, consider maintaining a hyper-engaged segment (e.g., interacted in the last 7 days) and sending less frequently to them with highly valued content to improve reputation.
• Monitor blocklists (blacklists): Regularly check if your sending IPs or domains have been listed on any blocklists (or blacklists), as this can contribute to content rejections by impacting overall sender trust. A list of email blacklists and their impact can be a valuable resource.
• Review DMARC reports thoroughly: Even if DMARC is passing, DMARC reports can offer insights into the overall authentication landscape of your domain, including potential issues with DMARC failures.

Key findings

• Layered filtering: Email deliverability relies on multiple layers of filtering, including authentication (SPF, DKIM, DMARC), sender reputation, and content analysis. Passing one layer does not guarantee success in others. Refer to RFC 8601 for DMARC specifics.
• Content analysis mechanics: Mail servers use complex algorithms to score email content based on various indicators such as keywords, URL reputation, attachment types, HTML structure, and image characteristics. These algorithms are proprietary and constantly updated.
• Error code meaning: The '558 5.7.1' SMTP error generally indicates a permanent failure related to content or policy, meaning the server explicitly rejected the message due to perceived policy violation or spam. The 'IB703' is an internal error code specific to Telstra/Bigpond, indicating a content-based spam detection.
• Dynamic reputation: ISPs continually adjust sender reputation based on real-time feedback, including spam complaints, engagement, and even the volume and velocity of sending. A shift in DMARC policy might bring more attention to traffic that was previously treated differently.

Key considerations

• Adherence to best practices: Beyond authentication, documentation often stresses compliance with general email best practices, including maintaining clean lists, managing opt-outs, and sending relevant content. This helps avoid email deliverability issues.
• ISP postmaster guidelines: ISPs like Telstra (Bigpond) often publish postmaster pages with specific guidelines for bulk senders. These pages can detail preferred sending behaviors, content types to avoid, and steps for delisting or inquiry.
• RFC compliance vs. practice: While RFCs define email standards, real-world ISP filtering practices can extend beyond strict RFC compliance, particularly in how they interpret spam. This gap means technical compliance isn't always enough. For further information, see RFC 5322 and real-world email.
• DMARC reporting analysis: While DMARC reports might show 'pass', they also provide aggregate data on volume and authentication outcomes that can subtly hint at reputation issues, even if not directly stating 'content rejected'.