How does sender domain vs IP hard bounce rate impact sender reputation with ISPs like Gmail?

Summary

Experts, marketers, and documentation sources agree that domain reputation is increasingly crucial for email deliverability, especially with Gmail. While IP reputation still matters, a poor domain reputation can lead to emails being marked as spam or blocked, even with a good IP reputation. High hard bounce rates negatively impact both IP and domain reputation, signaling poor list hygiene. Maintaining low bounce rates (ideally below 1-2%), using proper email authentication (SPF, DKIM, DMARC), ensuring positive recipient engagement (opens, clicks), and starting with small sending volumes to warm up the domain are vital. Understanding the specific reason for bounces (e.g., 'no such user' vs. domain block) and accurately processing bounce messages are essential. On shared IPs, bad sending practices from other users can negatively impact your reputation. Overall, a holistic approach that considers both technical aspects (authentication, bounce processing) and engagement metrics is key to successful email deliverability.

Key findings

  • Domain Dominance: Gmail primarily focuses on domain reputation for deliverability decisions.
  • Bounce Rate Matters: High hard bounce rates significantly damage sender reputation at both the IP and domain levels.
  • Engagement is Key: Positive recipient engagement (opens, clicks) is a critical factor for domain reputation.
  • Authentication is Essential: Proper email authentication (SPF, DKIM, DMARC) is crucial for protecting domain reputation and improving deliverability.
  • Contextual Bounces: The reason for a hard bounce (e.g., domain block vs. user unknown) impacts reputation differently.

Key considerations

  • Monitor Domain Reputation: Regularly monitor your domain reputation using tools like Google Postmaster Tools.
  • Maintain Low Bounce Rates: Implement strategies to minimize hard bounce rates, such as list hygiene and email verification.
  • Implement DMARC: Implement DMARC to protect your domain from spoofing and phishing attacks.
  • Analyze Bounce Reasons: Thoroughly analyze SMTP codes and text messages from bounces to identify and address the underlying causes.
  • Segment and Engage: Segment your email list and send targeted content to increase engagement and reduce the risk of bounces.
  • Process Bounces Accurately: Ensure robust bounce processing for IP/Domain reputation

What email marketers say
12Marketer opinions

ISPs, particularly Gmail, consider both IP and domain reputation when assessing sender reputation, but domain reputation is becoming increasingly important. High hard bounce rates negatively impact both IP and domain reputation, signaling poor list hygiene and potentially leading to blocked emails or spam folder placement. Maintaining low bounce rates (ideally below 1-2%), using proper email authentication (SPF, DKIM, DMARC), ensuring positive recipient engagement, and starting with small sending volumes to warm up the domain are crucial for building and maintaining a positive sender reputation. On shared IPs, bad sending practices from other users can negatively impact your reputation.

Key opinions

  • Domain vs IP: Gmail and other major ISPs prioritize domain reputation, though IP reputation still matters.
  • Hard Bounce Impact: High hard bounce rates negatively impact both IP and domain reputation.
  • Bounce Threshold: A generally accepted bounce rate range is below 1-2%.
  • Engagement Matters: Positive recipient engagement (opens, clicks) is crucial for domain reputation.
  • Shared IP Risks: On shared IPs, other users' sending practices can impact your reputation.

Key considerations

  • Monitor Bounce Rates: Regularly monitor bounce rates and implement strategies to minimize them.
  • Implement Authentication: Set up email authentication protocols (SPF, DKIM, DMARC) to improve deliverability.
  • Clean Email Lists: Maintain a clean and engaged email list to reduce bounce rates and improve engagement.
  • Warm Up Domains: Gradually warm up new sending domains to establish a positive sending history.
  • Check Reputation: Continually monitor your IP/Domain to understand any deliverability issues.
Marketer view

Email marketer from Reddit shares that while IP reputation matters, domain reputation is increasingly significant. Gmail and other major ISPs are placing more emphasis on domain-based metrics. Senders should focus on building a strong domain reputation through consistent sending practices, low bounce rates, and positive engagement signals.

May 2021 - Reddit
Marketer view

Email marketer from StackOverflow explains that sender IP, domain reputation, authentication (SPF, DKIM, DMARC), content, spam complaints, and bounce rates all affect reputation.

May 2022 - StackOverflow

What the experts say
5Expert opinions

Experts agree that hard bounce reasons and proper bounce processing are critical for maintaining a positive sender reputation. High hard bounce rates, particularly when combined with low engagement or specific block reasons (like domain-level blocks), severely damage domain reputation with ISPs like Gmail. Understanding the specific reason for bounces (e.g., 'no such user' vs. domain block) and accurately processing bounce messages are essential for identifying and addressing deliverability issues. Low open rates coupled with high bounces directly correlate to a bad reputation.

Key opinions

  • Bounce Reason Matters: The specific reason for a hard bounce significantly impacts sender reputation.
  • Domain Blocks Are Critical: Domain/subdomain blocks from ISPs require immediate cessation of mailing to avoid further reputation damage.
  • Engagement Amplifies Impact: High bounce rates coupled with low engagement exacerbate negative reputation effects.
  • Bounce Processing Is Key: Accurate and comprehensive bounce processing is crucial for understanding sender reputation.

Key considerations

  • Analyze Bounce Codes: Thoroughly analyze SMTP codes and text messages from bounces to determine the underlying cause.
  • Segment by Bounce Type: Differentiate between bounce types (e.g., user unknown vs. domain block) and implement appropriate actions.
  • Monitor Engagement: Track engagement metrics (open rates, click rates) in conjunction with bounce rates.
  • Process Bounces Accurately: Ensure robust and reliable bounce processing mechanisms are in place.
  • Focus on Sending List: Clean sending list
Expert view

Expert from Email Geeks explains to determine the specific bounce reason (domain block vs. user unknown). A domain/subdomain block from Google requires stopping mailing to avoid reputation damage and further describes the importance of analyzing SMTP codes and text messages from bounces to properly diagnose issues, providing examples of specific Google error messages and their corresponding fixes.

January 2024 - Email Geeks
Expert view

Expert from Word to the Wise explains that bounce processing is a complex task but should be set up correctly. Getting the bounces processed badly means you do not know the correct IP/Domain reputation.

December 2024 - Word to the Wise

What the documentation says
4Technical articles

Documentation from Google, Microsoft, and Dmarc.org emphasizes that domain reputation is a primary factor for email deliverability, especially with Gmail. High bounce rates negatively affect sender reputation, leading to emails being marked as spam or blocked. Proper email authentication (DMARC) and diligent management of subscriber lists are crucial for maintaining a good reputation. Understanding SMTP status codes helps pinpoint the causes of bounces, enabling targeted remediation.

Key findings

  • Domain Focus: Gmail primarily evaluates sender reputation based on the domain.
  • Bounce Impact: High bounce rates negatively impact sender reputation, affecting deliverability to major ISPs.
  • Authentication Essential: DMARC and other email authentication methods are critical for protecting domain reputation.
  • SMTP Codes Informative: SMTP status codes provide valuable information for diagnosing bounce issues.

Key considerations

  • Prioritize Domain Reputation: Focus on building and maintaining a strong domain reputation through best practices.
  • Minimize Bounce Rates: Implement strategies to keep bounce rates low, such as list hygiene and targeted sending.
  • Implement DMARC: Deploy DMARC and other email authentication protocols to prevent spoofing and phishing.
  • Analyze Bounce Causes: Regularly review SMTP status codes to understand the reasons for bounces and address underlying issues.
Technical article

Documentation from Microsoft explains that high bounce rates negatively impact sender reputation, affecting email deliverability to Outlook.com and other Microsoft email services. Implementing email authentication and managing subscriber lists are key components of maintaining a good sender reputation. Microsoft also states that the source is considered when determining the reputation - either the sending IP or domain.

July 2021 - Microsoft 365 documentation
Technical article

Documentation from Dmarc.org explains that Domain-based Message Authentication, Reporting & Conformance (DMARC) is critical to protecting your email and domain reputation.

February 2022 - Dmarc.org