Why are emails to Bigpond bouncing or being marked as spam?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Apr 2025
Updated 16 Aug 2025
7 min read
Experiencing email bounces or messages being marked as spam when sending to Bigpond.com (Telstra) recipients can be incredibly frustrating. It is a common challenge for many senders, even when sending legitimate communications like customer support replies or transactional emails. You might see specific bounce messages such as 558 5.7.1 Message content rejected due to suspected spam. IB704x, indicating that their servers are actively blocking your mail.
Even with an unchanged email strategy, a sudden increase in these issues suggests that factors beyond your immediate sending practices are at play. It points to a need to delve deeper into why Bigpond's (Telstra's) filters are flagging your emails.
Understanding Bigpond's filtering challenges
Bigpond, as an email service provider, is known for its strict filtering mechanisms. This is often an attempt to protect its users from unsolicited bulk email, but sometimes legitimate mail can get caught in the crossfire. One common observation is that Bigpond's infrastructure can struggle with higher volumes of email, leading to throttling or outright rejections.
This challenge is exacerbated because Bigpond is, in some respects, an older and less actively updated platform compared to others. Its servers might not always be able to handle the same email volume as larger providers, resulting in bounces even for small, targeted sends. The system can become overwhelmed, leading to delivery failures that appear arbitrary.
A key factor in Bigpond's email blocking is its use of denylist services to identify and block mail from suspected spammers, as mentioned by Google support. This means that if your sending IP address or domain appears on any of the blocklists (or blacklists) Bigpond consults, your emails will likely bounce. This is a common method ISPs use to combat spam and protect their users.
Identifying Bigpond's filtering challenges
Legacy Infrastructure: Bigpond's older systems may not handle modern email volumes efficiently, leading to throttling and bounces.
Strict Spam Filters: Their filters are often highly sensitive, catching legitimate emails, especially if content or sending patterns trigger flags.
IP and Domain Blocklists: If your sending IP or domain is listed on a blocklist (or blacklist), Bigpond might automatically reject your messages.
Common reasons for Bigpond bounces and spam classification
Several factors can cause your emails to bounce or be marked as spam by Bigpond. One of the most significant is your sender reputation. Even if your internal strategy hasn't changed, your sending reputation can degrade over time due to various factors, such as increased complaints, sending to old or invalid addresses, or being caught in spam traps. This impacts how Bigpond views your emails.
Content-based filtering is another major culprit. The error message Message content rejected due to suspected spam explicitly points to this. This happens when certain words, phrases, or even specific URLs within your email are flagged as suspicious because they are often associated with spam. It's not just about obvious spammy content, but also about how your URLs are perceived, especially if they have been seen frequently in spam campaigns. You can find more information about why Bigpond emails bounce due to content in our dedicated guide.
Furthermore, a lack of proper email authentication can severely impact your deliverability. Bigpond, like most major ISPs (internet service providers), relies heavily on SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) to verify the legitimacy of incoming emails. If these records are misconfigured or missing, your emails are much more likely to be seen as spoofed or suspicious, leading to bounces or spam folder placement. Learn more about DMARC, SPF, and DKIM in our simple guide.
Common causes of bounces
Low Sender Reputation: Complaints, invalid addresses, or spam trap hits can lower your standing.
Content Filters: Spammy phrases, suspicious links, or certain file attachments trigger rejections. The error 558 5.7.1 from Bigpond often points to this, as noted by JustAnswer.
IP or Domain Blocklisting: Your sending IP or domain may appear on a public or private email blacklist, leading to rejections. Understand how email blacklists actually work.
Ensuring proper authentication
SPF Configuration: Authorizes sending servers for your domain. Incorrect SPF can cause rejections.
DMARC Policy: Enforces SPF and DKIM, telling receiving servers how to handle emails that fail authentication.
Practical steps to improve deliverability to Bigpond
When facing Bigpond email issues, a proactive approach to troubleshooting is essential. First, review your bounce messages carefully. The error codes and accompanying text often provide clues about the specific reason for rejection. For example, 558 5.7.1 points to content, while others might indicate an IP blocklist or a temporary issue. More broadly, an understanding of email delivery errors is invaluable.
Next, verify your email authentication records. Use a free online email testing tool to check your SPF, DKIM, and DMARC setup. Ensure all records are correctly published and aligned. Many deliverability issues stem from simple misconfigurations here. Monitoring your blocklist status can also reveal if your sending IP or domain has been compromised or listed.
If you're sending a high volume of emails to Bigpond addresses, consider adjusting your sending rate. Bigpond's servers are known to throttle or reject emails if the volume is too high, even if your reputation is good. Implement slower sending rates specifically for Telstra/Bigpond domains to accommodate their infrastructure limitations. This might involve setting up specific sending queues or throttling rules within your email sending platform.
Finally, ensure your email content is clean and doesn't contain common spam triggers. This includes avoiding excessive capitalization, too many images, broken links, or suspicious formatting. Regularly review your email templates and text to ensure they meet deliverability best practices.
Long-term strategies and prevention
Long-term success in email deliverability, especially with challenging providers like Bigpond, requires consistent effort. One crucial aspect is maintaining a healthy email list. Regularly clean your list to remove inactive or invalid addresses, which can otherwise act as spam traps or simply lead to excessive bounces. Sending to a clean, engaged list signals to ISPs that your mail is wanted, improving your sender reputation.
Implement and monitor a robust DMARC policy. DMARC provides valuable insights into how your emails are performing across the internet, including with Bigpond. By analyzing DMARC reports, you can identify authentication failures and sources of unauthorized mail, allowing you to take corrective action. This helps solidify your sending domain's trustworthiness. Our DMARC monitoring tools can assist with this.
Focus on email engagement. Positive engagement signals, such as opens, clicks, and replies, tell ISPs that your recipients value your emails. Conversely, high complaint rates or low engagement can negatively impact your sender reputation, making it harder to reach the inbox. Encourage recipients to add you to their address book and make it easy to manage subscriptions to reduce spam complaints. Following a comprehensive guide on email deliverability can help.
Best practices for consistent deliverability
List Hygiene: Regularly remove unengaged subscribers and invalid addresses to avoid spam traps.
Authentication Monitoring: Continuously monitor your SPF, DKIM, and DMARC records for proper setup and alignment.
Engagement Focus: Prioritize sending relevant content to engaged subscribers to build positive reputation.
Views from the trenches
Dealing with Bigpond's unique email filtering quirks can be challenging. Here's what deliverability professionals and marketers have observed and suggest, offering insights from real-world experiences.
Best practices
Actively monitor your sender reputation and IP status, not just your email strategy.
Adjust sending volume and rates for Bigpond domains to prevent throttling.
Maintain perfectly configured SPF, DKIM, and DMARC records.
Regularly clean your email lists to remove inactive Bigpond addresses.
Common pitfalls
Assuming an unchanged email strategy means a constant sender reputation.
Ignoring specific bounce messages for Bigpond recipients.
Sending high volumes to Bigpond, overwhelming their older infrastructure.
Neglecting email list hygiene, leading to spam traps and lower engagement.
Expert tips
Consider engaging with a dedicated deliverability expert if issues persist.
Segment your Bigpond recipients for specialized sending patterns.
Focus on content relevance and personalization to boost engagement with Bigpond users.
Explore Bigpond's (Telstra's) support channels, though direct contact can be difficult.
Expert view
Expert from Email Geeks says that suspected spam content bounces could mean your URLs are flagged as frequently seen in spam, not just your overall mail content.
2021-04-26 - Email Geeks
Expert view
Expert from Email Geeks says that an unchanged strategy does not mean your sender reputation has not been degrading over time.
2021-04-26 - Email Geeks
Putting an end to Bigpond bounces
Navigating Bigpond's (Telstra's) email filtering can be a complex task, but by understanding their unique challenges and implementing best practices, you can significantly improve your deliverability rates. The key lies in a multi-faceted approach focusing on sender reputation, proper authentication, appropriate sending volumes, and engaging content.
Regularly monitoring your email performance, staying informed about email authentication standards, and maintaining a healthy sending environment are crucial steps. While some issues may require direct communication with Bigpond, a strong foundational deliverability strategy will minimize bounces and ensure your legitimate emails reach their intended recipients.
