Why am I getting soft bounces from Windstream, TDS, CenturyTel, Hughes and Zoom Internet?

Key findings

• Shared bounce reason: All listed ISPs are returning a 554 5.7.1 Message blocked due to spam content in the message bounce code, suggesting a common underlying cause related to content filtering or reputation.
• Consistent sender behavior: The sender reports being a longtime sender of transactional emails, with great engagement and no recent content changes, indicating the issue may not originate from a sudden shift in sending practices.
• Filtering solution commonality: There's a strong possibility that these ISPs leverage a shared anti-spam or content filtering service, such as VADE Secure (indicated by the VI-1 tag) or Cloudmark, even if their underlying Mail Transfer Agents (MTAs) differ.
• Reputation shift: The issue is likely tied to a recent negative shift in sender IP or domain reputation as perceived by these shared filtering systems, rather than a specific content problem.

Key considerations

• Analyze bounce codes: Detailed examination of the full bounce message is crucial, especially diagnostic codes like [VI-1], which can point to specific anti-spam vendors.
• Check content triggers: Even if content hasn't changed, certain keywords or formatting might be newly flagged by updated filtering algorithms. For a deeper dive into soft bounce reasons, refer to this guide on hard versus soft bounces.
• Monitor sender reputation: Regularly check your IP and domain reputation. A sudden decline could explain synchronized blocklisting across multiple ISPs. Tools for understanding your email domain reputation are invaluable here.
• Contact ISP postmasters/abuse desks: Reach out directly to the abuse or postmaster contacts for each domain or the suspected filtering service (e.g., VADE Secure's sender tool) to investigate and request delisting.
• Review authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured and aligned. A common issue leading to blocks is misconfiguration of these authentication protocols, which can be explored in our simple guide to DMARC, SPF, and DKIM.

Key opinions

• Consistency of problem: Marketers frequently observe consistent soft bounce behavior across seemingly unrelated smaller ISPs, suggesting a shared mechanism or provider for their email infrastructure or filtering.
• Bounce message insights: The diagnostic codes within bounce messages are critical. For instance, the [VI-1] code immediately points to VADE Secure, a common filtering solution.
• Focus on content: Even with no content changes, content-related bounce messages indicate that the filtering system believes the message contains spam, potentially due to updated detection algorithms or an increase in spam volume impacting shared infrastructure.
• Impact on transactional email: When transactional emails, which typically have high engagement and low spam complaints, start bouncing, it's a strong signal of an external filter issue rather than internal sending hygiene.

Key considerations

• Identify common filtering: The first step is to identify if a common filtering provider is used across all affected ISPs. This often requires digging into bounce headers and online resources. If you are experiencing similar issues with Cox.net, you may find our article on Cox.net soft bounces helpful.
• Utilize sender tools: Many anti-spam vendors (like VADE Secure) offer sender tools or portals for senders to check their IP/domain status and request delisting.
• Engage with postmasters: Direct communication with the postmaster or abuse desk of the problematic ISPs can provide specific insights and pathways to resolution. This is a crucial step for resolving blocklisting issues with small ISPs.
• Review email headers: Beyond the bounce code, full email headers can reveal additional details about the path of the email and which systems might be intervening. Understanding email soft bounces and how to fix them involves a thorough analysis.

Key opinions

• VADE Secure identification: Experts quickly identify VI in the bounce code as an indicator for VADE Secure, a common anti-spam vendor used by various ISPs.
• Cloudmark usage: Some experts recall that Windstream and CenturyTel, in particular, have historically used Cloudmark for their spam filtering, reinforcing the idea of shared services.
• Shared infrastructure impact: Even if ISPs use different MTAs, they can still share common filtering or reputation services, leading to synchronized email deliverability issues for senders.
• Abuse portal efficiency: Experts recommend using official abuse portals or sender tools provided by the ISPs or their filtering vendors as the most effective way to address blocklisting or deliverability issues.

Key considerations

• Verify filtering vendor: Confirm the specific filtering vendor responsible for the blocks by cross-referencing diagnostic codes with known vendor identifiers. This targeted approach can streamline the resolution process.
• Utilize vendor-specific tools: If a vendor like VADE Secure is identified, use their dedicated sender tool https://sendertool.vadesecure.com/ to check your IP/domain status and submit delisting requests. This is often more effective than general ISP contact points.
• Consider shared resources: Even if the MTAs are different, assess other shared resources that could impact deliverability, such as common blacklists or shared IP spaces. Our in-depth guide to email blocklists can offer further context.
• Proactive reputation management: Implement robust practices to maintain a high sender reputation to mitigate risks of being caught by shared filtering systems. Regularly check for signs of emails going to spam and address them promptly.

Key findings

• Bounce code interpretation: A 554 5.7.1 error typically indicates a permanent rejection due to policy reasons, often related to spam or sender reputation, even if it's called a 'soft bounce' in context of a series of such failures.
• Third-party filtering: Many smaller ISPs and regional providers integrate with, or fully outsource to, established anti-spam solutions like VADE Secure or Cloudmark. These services maintain their own reputation databases and filtering rules.
• Content and reputation: Bounce messages referencing 'spam content' can be triggered by actual content, but more often by a low sender reputation (IP or domain) that causes the filtering system to apply stricter content checks or block messages outright.
• Transactional email sensitivity: While transactional emails are generally high-priority, they are not immune to filtering. Any perceived threat, even if erroneous, can lead to blocks to protect user inboxes.

Key considerations

• Adhere to RFC standards: Ensure your email sending practices strictly adhere to relevant RFCs (Request for Comments) for email, as deviations can lead to silent blocks or rejections. For more information, read what RFC 5322 says vs. what actually works.
• Maintain domain reputation: Continuously monitor and improve your domain's sending reputation. ISPs (and their filtering partners) rely heavily on this. You can utilize resources like the Ultimate Guide to Google Postmaster Tools V2.
• Implement DMARC, SPF, DKIM: Strong email authentication is a foundational requirement for deliverability. ISPs use these protocols to verify sender legitimacy. Make sure your DMARC, SPF, and DKIM are correctly set up.
• Leverage feedback loops: Sign up for any available feedback loops (FBLs) offered by ISPs or their anti-spam partners. FBLs notify you when your emails are marked as spam, allowing you to quickly identify and address issues.
• Consult ISP postmaster pages: While smaller ISPs may have less detailed documentation, checking their official postmaster or abuse pages for specific guidelines and contact information is crucial. Refer to any general RFCs related to SMTP and bounce handling for broader understanding.