Summary
Elevated email blocks and bounces, alongside bot-driven unsubscribes, stem from a confluence of factors including poor list hygiene (invalid addresses, spam traps, outdated contacts), compromised sender reputation (blacklisting, inadequate authentication - SPF, DKIM, DMARC), fluctuations in recipient behavior, and potential spam attacks. Bot-initiated unsubscribes, often triggered by email scanners, can be mitigated through CAPTCHAs or double opt-in. Additionally, excessive sending volumes can trip spam filters. Correct bounce processing is vital for maintaining a positive sender image. Addressing these issues holistically, including ongoing list maintenance, robust authentication protocols, bot mitigation strategies, and careful analysis of bounce codes, is essential for improving deliverability and ensuring secure email communication.
Key findings
- List Hygiene: Poorly maintained email lists contribute significantly to increased bounces and blocks.
- Sender Reputation: A negative sender reputation has a direct and severe impact on email deliverability.
- Bot Activity: Automated bots are actively unsubscribing users and causing other issues.
- Authentication: Lack of proper authentication results in email deliverability problems.
- Sending Volume: Excessive sending of emails can be flagged as SPAM by providers.
- Recent ISP Changes: Recent changes by Yahoo and Gmail may be a cause
Key considerations
- Regularly Clean Email Lists: Routinely remove invalid, inactive, and problematic email addresses from your sending lists.
- Implement Strong Authentication: Ensure SPF, DKIM, and DMARC records are correctly configured to authenticate your email sending.
- Deploy Bot Mitigation Strategies: Utilize CAPTCHAs, double opt-in, and other techniques to prevent automated unsubscribes.
- Manage Sending Volume: Gradually ramp up sending volume to avoid triggering spam filters.
- Process Bounces: Implement a system for processing both soft and hard bounces
- Monitor Subscriber Complaint Rates: Make sure you implement a feedback loop
What email marketers say
12 marketer opinions
The reasons for higher than normal email blocks and bounces include list quality issues (invalid addresses, spam traps, outdated lists), sender reputation problems (being blacklisted, poor authentication), changes in recipient habits, and potential spam attacks. Bot unsubscribes are often caused by email scanners clicking unsubscribe links, and can be mitigated with CAPTCHAs or double opt-in. Sending too many emails can also trigger spam filters, suggesting a gradual ramp-up of send rates. Processing bounce messages correctly is key to maintaining a good sending reputation. Monitoring unsubscribe patterns and implementing a feedback loop can further improve deliverability.
Key opinions
- List Quality: Poor list quality (invalid addresses, spam traps, outdated lists) is a major contributor to higher bounces and blocks.
- Sender Reputation: A damaged sender reputation, potentially leading to blacklisting, significantly impacts deliverability.
- Bot Unsubscribes: Email scanners and bots are triggering unsubscribes, requiring mitigation strategies.
- Sending Volume: Sending too many emails too quickly can trigger spam filters.
- Yahoo and Gmail Issues: Recent issues with Yahoo and Gmail may also be contributing to deliverability problems.
Key considerations
- List Hygiene: Regularly clean and validate your email lists to remove invalid or inactive addresses.
- Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) to improve sender reputation.
- Unsubscribe Mitigation: Implement measures like CAPTCHAs or double opt-in to prevent bot unsubscribes.
- Send Rate Ramp-Up: Gradually increase sending volume to avoid triggering spam filters.
- Monitor Unsubscribe Patterns: Track unsubscribe patterns to identify and address potential bot activity or other issues.
- Bounce Processing: Correctly process bounce messages to identify and remove invalid addresses
Marketer view
Email marketer from StackOverflow mentions that one-click unsubscribe can be exploited by bots, as some email clients and security scanners automatically trigger the unsubscribe link for every email. They suggest monitoring unsubscribe patterns and looking for unusual activity, like multiple unsubscribes from the same IP address in a short period.
3 Dec 2024 - StackOverflow
Marketer view
Marketer from Email Geeks says that while looking at logs, they are having subscribers go through every message sent to them in the past month and complain on all of them at one time within seconds of each complaint. These subscribers have been on the list for a while and have interacted positively. Suggesting it is a possible complaint bombing by a bot.
20 Mar 2024 - Email Geeks
What the experts say
2 expert opinions
Correctly processing bounces and mitigating bot traffic are crucial components of email deliverability. Ignoring hard bounces harms sender reputation due to continued sending to invalid addresses. A comprehensive strategy should address both bounce management and the prevention of automated bot activity.
Key opinions
- Bounce Processing: Incorrectly handling bounces (especially hard bounces) negatively impacts sender reputation and deliverability.
- Bot Mitigation: Failing to mitigate automated bot traffic in email campaigns will have a negative impact.
Key considerations
- Implement Bounce Processing: Establish a process for accurately identifying and removing bounced email addresses from sending lists.
- Mitigate Bot traffic: Implement safeguards to protect against spam bots.
Expert view
Expert from Spam Resource responds that mitigating automated bot traffic needs to be a key part of any email marketing campaign.
24 Oct 2024 - Spam Resource
Expert view
Expert from Word to the Wise explains that correctly processing bounces is critical for maintaining a good sending reputation. Ignoring hard bounces results in continued sending to invalid addresses, impacting deliverability. She also recommends implementing a feedback loop to handle complaints effectively.
19 Nov 2024 - Word to the Wise
What the documentation says
4 technical articles
Email blocks and bounces can be caused by sender reputation issues, authentication failures (SPF, DKIM, DMARC), high spam complaint rates, sending unsolicited emails, invalid recipient addresses, server problems, content filters, infrastructure and quota issues, and bots and malware. Reviewing bounce codes and following sender guidelines are crucial for troubleshooting and improving deliverability; patching systems helps protect from bots and malware.
Key findings
- Sender Reputation: Poor sender reputation is a primary cause of email blocks.
- Authentication: Authentication failures (SPF, DKIM, DMARC) contribute to deliverability problems.
- Bounce Reasons: Bounces result from various technical and content-related issues.
- Bot/Malware Impact: Bots and malware can negatively affect email deliverability and data security.
Key considerations
- Follow Guidelines: Adhere to sender guidelines provided by major email providers (e.g., Google, Microsoft).
- Analyze Bounce Codes: Carefully analyze bounce codes to identify the root causes of delivery failures.
- System Security: Keep systems patched and secure to prevent bot/malware activity.
- Implement Authentication: Implement robust email authentication to improve deliverability.
Technical article
Documentation from RFC 3464 (Bounce Message Format) explains that bounces can result from infrastructure problems, quota issues, invalid addresses, policy reasons and content issues. The recommendation is to read the response codes.
19 May 2025 - RFC 3464
Technical article
Documentation from Spamhaus explains that bots and malware can cause issues. It is essential to keep your system patched to block bad traffic and ensure that all customer data is safe.
29 Nov 2023 - Spamhaus
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