Summary
The discussion around asynchronous bounces reveals a consensus that they are present and impact email deliverability. While some suggest they never disappeared, especially concerning forwarded emails (Comcast), others highlight their return with a stronger emphasis on authentication. Experts have noted that the IETF DKIM mailing list is the place to follow DKIM2 discussion. High bounce rates, including asynchronous, negatively affect sender reputation. Effective management includes maintaining list hygiene, using bounce processing tools, monitoring sender reputation, employing email verification APIs, and understanding bounce codes. DMARC failure reporting can also provide insights.
Key findings
- Asynchronous Bounce Status: Asynchronous bounces are an ongoing issue, sometimes occurring with forwarded mail, and more authenticated now.
- DKIM2 Discussion Venue: The IETF DKIM mailing list will host the public discussion on DKIM2.
- Negative Impact of Bounces: High bounce rates, driven by asynchronous bounces, damage sender reputation and hurt deliverability.
- Importance of Hygiene: List hygiene remains critical for controlling bounce rates and preventing deliverability issues.
- Need for Bounce Processing: Effective tools for identifying and processing bounces are a necessity.
- Value of Header Configuration: Correct configuration of Return-Path/Sender headers is important for bounce processing.
Key considerations
- Manage Bounce Rates: Implement strategies to manage and reduce bounce rates to protect sender reputation.
- Maintain List Hygiene: Regularly clean and validate email lists to remove inactive or problematic addresses.
- Monitor Deliverability: Continuously monitor email deliverability metrics to identify and address any issues.
- Implement Authentication: Implement and properly configure DKIM/SPF records to improve sender authentication.
- Utilize Verification Tools: Consider using email verification tools to identify and remove invalid email addresses before sending.
- Stay Informed About DKIM2: Monitor for IETF mailing lists regarding DKIM2 for future updates.
- Comcast Consideration: Pay special attention to Comcast-specific bounce issues due to their forwarding practices.
What email marketers say
10 marketer opinions
The re-emergence of asynchronous bounces presents challenges for email marketers. While some sources indicate they never truly disappeared, particularly concerning forwarded mailboxes, a consensus exists regarding their negative impact on sender reputation and deliverability. Managing overall bounce rates, including these asynchronous events, is vital. Strategies include proactive list hygiene, implementing robust bounce processing mechanisms, closely monitoring sender reputation metrics, and potentially utilizing email verification APIs to identify and remove problematic addresses before sending.
Key opinions
- Asynchronous Bounces Persist: Asynchronous bounces, while not always readily apparent, continue to occur, particularly with forwarded email accounts.
- Deliverability Impact: High bounce rates, inclusive of asynchronous bounces, significantly degrade sender reputation, leading to reduced deliverability and increased spam filtering.
- List Hygiene Importance: Maintaining a clean email list through regular hygiene practices is crucial for mitigating the impact of bounces.
- Bounce Processing: Robust bounce processing mechanisms are necessary to identify and handle asynchronous bounces effectively, despite the challenges they present.
- Sender Reputation Monitoring: Continuous monitoring of sender reputation is essential to detect and address deliverability issues stemming from asynchronous bounces.
Key considerations
- List Hygiene Strategy: Implement a comprehensive list hygiene strategy that includes regular removal of inactive or problematic email addresses.
- Bounce Processing Implementation: Develop or integrate a robust bounce processing system capable of accurately identifying and classifying both synchronous and asynchronous bounces.
- Sender Reputation Monitoring Tools: Utilize sender reputation monitoring tools to proactively track and address any negative impacts on deliverability.
- Email Verification API: Consider using an email verification API to validate email addresses before sending, reducing the likelihood of bounces.
- Comcast bounces: Based on Comcast data, asynchronous bounces never left and are pretty much all for recipients who are forwarding their mailbox, which makes perfect sense why they would be OOB.
Marketer view
Email marketer from Litmus emphasizes the importance of monitoring sender reputation. Asynchronous bounces can affect sender reputation and deliverability, therefore monitoring and managing them is essential.
20 Aug 2021 - Litmus
Marketer view
Email marketer from Email on Acid highlights the negative impact of high bounce rates on email deliverability. Asynchronous bounces need to be monitored to prevent damage to sender reputation.
12 Jul 2021 - Email on Acid
What the experts say
5 expert opinions
Experts indicate that asynchronous bounces have returned, albeit with some changes in their nature from an ESP infrastructure perspective. Discussions surrounding DKIM2 are expected to occur on the existing IETF DKIM mailing list, though a private list may also exist. Accurately interpreting bounce codes is crucial, and insights into authentication issues, potentially related to bounces, can be derived from DMARC failure reporting.
Key opinions
- Asynchronous Bounces Return: Asynchronous bounces are back in email marketing, with authentication playing a larger role.
- DKIM2 Discussion Location: The public discussion for DKIM2 will take place on the existing IETF DKIM mailing list.
- Bounce Code Interpretation: Proper interpretation of bounce codes is essential for understanding the reasons behind bounces.
- DMARC Insights: DMARC failure reporting can offer insights into authentication problems which may affect bounces.
Key considerations
- Stay Informed on DKIM2: Monitor the IETF DKIM mailing list for updates and discussions regarding DKIM2.
- Understand Bounce Codes: Develop a thorough understanding of bounce codes to effectively diagnose and address deliverability issues.
- Review DMARC Reporting: Regularly review DMARC aggregate and forensic reports to identify and resolve authentication problems.
- Private DKIM2 list: Note that there might be some private lists that exist that you will not have access to regarding DKIM2 discussion.
Expert view
Expert from Spam Resource discusses bounce messages and states that bounce messages can be delayed or lost and that it is important to correctly interpret the bounce codes as the details vary.
2 Dec 2022 - Spam Resource
Expert view
Expert from Email Geeks states that asynchronous bounces are back and while it's not the same as before, from an ESP infrastructure level it’s close, and more authenticated.
26 Oct 2023 - Email Geeks
What the documentation says
4 technical articles
Technical documentation defines asynchronous bounces as out-of-band notifications requiring specific handling. The IETF DKIM Working Group maintains standards and discussion forums related to DKIM, including potential updates like DKIM2. Understanding DKIM, as described on Wikipedia, is essential for email authentication. Proper configuration of 'Return-Path' and 'Sender' headers, along with SPF records, is crucial for accurate bounce processing.
Key findings
- Asynchronous Bounces Defined: Asynchronous bounces are out-of-band notifications requiring dedicated processing.
- DKIM Standardization: The IETF DKIM Working Group standardizes and maintains DKIM protocols.
- DKIM Overview: Wikipedia offers a comprehensive overview of DKIM and its role in email authentication.
- Bounce Processing Headers: Correctly setting 'Return-Path' and 'Sender' headers is critical for bounce processing, alongside SPF records.
Key considerations
- RFC 6114 Compliance: Ensure your systems handle asynchronous bounces according to RFC 6114 specifications.
- Monitor IETF DKIM: Stay updated with the IETF DKIM Working Group's activities and updates, including DKIM2 developments.
- Implement DKIM Correctly: Implement DKIM properly, referencing the documentation provided to improve email authentication.
- Verify Header Settings: Carefully verify 'Return-Path' and 'Sender' header configurations to ensure proper bounce handling and prevent deliverability issues.
Technical article
Documentation from IETF DKIM Working Group maintains the DKIM (DomainKeys Identified Mail) standard. Information on DKIM discussion forums and updates, including DKIM2, will be found here.
15 Jul 2023 - ietf.org
Technical article
Email Documentation from AuthSMTP answers explains the importance of the 'Return-Path' and 'Sender' header to ensure that bounce emails are correctly delivered and that you have an SPF record setup.
31 Mar 2025 - AuthSMTP
Can 'invalid recipient' bounce messages be false positives and what should I do about it?
Do soft bounces affect email deliverability and sender reputation?
How are email bounce rates calculated and what is considered a good bounce rate?
Is there a standard format for late bounce error messages and how are asynchronous bounces best handled?
What are common terms for the envelope.from domain in email marketing?
What is a good bounce rate percentage to aim for in email marketing?
