What bounces are email marketers seeing?

Key findings

• Hard bounces: These are permanent delivery failures caused by non-existent email addresses or invalid domains. They significantly harm sender reputation and should be promptly removed.
• Soft bounces: These indicate temporary issues, such as a full mailbox or server downtime. While less critical, repeated soft bounces can still impact deliverability over time.
• Acceptable rates: Many marketers aim for a bounce rate below 2%. Higher rates can signal problems with list hygiene or content.
• ISP sensitivity: Internet Service Providers (ISPs) closely monitor bounce rates as a key indicator of sender quality. High bounce rates can lead to blocklisting or reduced inbox placement.

Key considerations

• List hygiene: Regularly cleaning your email list to remove invalid or inactive addresses is paramount.
• Monitoring tools: Utilize analytics to track bounce rates and identify specific bounce codes for troubleshooting.
• Segmentation: Segmenting your audience can help target more engaged users, reducing the likelihood of bounces.
• Content quality: Poor content or spammy practices can indirectly lead to bounces if recipients mark emails as spam, impacting reputation.
• Email service provider management: Understand how your ESP (Email Service Provider) handles soft and hard bounces, as practices vary.
• Understanding bounce types: Distinguish between soft bounces versus hard bounces for appropriate action.

Key opinions

• List quality: Many believe that list quality is the primary driver of high bounce rates.
• Acceptable rates: A common benchmark for a healthy bounce rate is 2% or lower. Anything above 3% is generally considered a red flag by email marketers, as noted by SocketLabs.
• Immediate action: Hard bounces should trigger immediate removal from the subscriber list to protect sender reputation.
• Soft bounce tolerance: Marketers often allow a few attempts for soft bounces before considering removal.

Key considerations

• Validation practices: Implementing real-time email validation at signup helps prevent bad addresses from entering the list.
• Engagement segmentation: Segmenting based on engagement can help identify and suppress inactive subscribers who might turn into bounces or spam traps.
• Bounce code analysis: Understanding specific SMTP bounce codes (e.g., 550, 421) provides insights into the root cause of delivery failures.
• Monitoring trends: Consistent monitoring of bounce rates is necessary to catch sudden spikes that indicate a problem, as discussed in useful bounce data for email marketing.

Key opinions

• Reputation impact: High bounce rates, especially hard bounces, signal poor list quality or abusive sending practices to ISPs, leading to deliverability problems.
• Thresholds: While 2% is a general benchmark, some ISPs may have stricter internal thresholds before applying throttling or blocklisting.
• Proactive suppression: Automated suppression of hard bounced addresses is not just good practice, it is a necessity for maintaining a healthy sending domain.
• Authentication: Proper email authentication (SPF, DKIM, DMARC) helps ISPs trust your sending, but it doesn't prevent bounces from bad addresses. These protocols are crucial for email authentication.

Key considerations

• Data accuracy: Focus on data quality at the point of collection to minimize invalid entries from the start.
• Bounce classification: Ensure your ESP correctly classifies and handles different bounce types.
• Feedback loops: Leverage ISP feedback loops (FBLs) to identify and remove users who mark your emails as spam, which can prevent future bounces.
• ISP-specific behavior: Understand that ISPs (like Gmail, Outlook) have unique bounce behaviors and implement different throttling rules. Consulting resources like Word to the Wise can provide valuable insights.

Key findings

• Permanent vs. temporary: Documentation clearly differentiates between hard bounces (permanent failure, e.g., invalid address) and soft bounces (temporary failure, e.g., full mailbox), as outlined by Moosend.
• Sender reputation: Many resources highlight that high bounce rates negatively impact sender reputation, leading to lower inbox placement or even blacklisting.
• Automatic suppression: Best practice documentation advises automatic removal of hard bounces to protect sending infrastructure and reputation.
• Bounce codes: SMTP bounce codes (e.g., 5xx for hard, 4xx for soft) provide detailed reasons for delivery failures, guiding troubleshooting efforts.

Key considerations

• List decay: Documentation often mentions the natural decay of email lists, necessitating regular validation to reduce bounces.
• Bounce classification rules: Understanding how various ESPs classify and count bounces is essential for accurate reporting.
• Threshold management: Setting internal thresholds for acceptable bounce rates helps proactive management and preventing deliverability issues, as discussed in how bounce rates are calculated.
• Spam traps: Documentation frequently warns about spam traps, which can result in hard bounces and severe reputation damage if hit.