How can I reduce soft bounces after a one-day email volume spike?

Key findings

• Volume spikes: A single day volume spike can negatively affect sender reputation, leading to sustained high soft bounce rates, even if subsequent sending volume returns to normal. This often means ISPs are throttling your mail.
• Soft bounces as warnings: High soft bounce rates are not just temporary delivery issues, they are often a signal that your mail stream reputation is being scrutinized, potentially leading to more severe deliverability problems like inbox placement failures or blocklisting.
• ISP-specific issues: Soft bounces are rarely uniform across all ISPs. Identifying which specific ISPs are generating the deferrals is crucial for targeted mitigation efforts.
• Engagement matters: While sending to engaged users (e.g., those who have opened recently) is a good practice, a sudden surge in volume can still trigger ISP scrutiny regardless of engagement levels.

Key considerations

• Identify problem ISPs: Analyze your bounce reports to pinpoint which Internet Service Providers (ISPs) are consistently deferring your emails. This data is critical for focused adjustments.
• Gradual volume reduction: For affected ISPs, slowly reduce your sending rate until the soft bounce rate decreases to an acceptable level. This process is similar to email volume management after a reputation hit.
• Maintain consistent sending: After adjusting volume, ensure a steady and predictable sending pattern. ISPs prefer consistent behavior over erratic spikes. This helps in recovering email domain and IP reputation.
• Monitor deliverability metrics: Continuously track your deliverability metrics, including soft bounce rates, inbox placement, and engagement, to gauge the effectiveness of your adjustments. For additional tips, consider these ways to reduce email bounce rate.

Key opinions

• Impact of spikes: A one-day volume spike, even with engaged users, can damage reputation, leading to continued soft bounces (deferrals) across subsequent campaigns.
• Audience quality: While focusing on engaged users is good, marketers still need to address the impact of a spike on overall sender reputation with ISPs. Old or unengaged addresses should always be excluded.
• Soft bounce meaning: Many marketers interpret soft bounces as deferrals, meaning emails are temporarily rejected but retried later. However, consistent deferrals are a sign of underlying reputation issues.
• Throttling indicators: High soft bounce rates are often a direct result of ISPs throttling your email stream due to suspicion stemming from the volume spike.

Key considerations

• Identify problem ISPs: Marketers should delve into their bounce data to see which specific ISPs are causing the soft bounces, as this points to where reputation has been most affected.
• Adjust sending rates: Once problematic ISPs are identified, marketers should consider incrementally reducing the sending volume to those specific domains until the deferral rates subside. This is critical for troubleshooting high soft bounce rates.
• Review subscriber engagement: Even with an existing sunset policy, re-evaluate and potentially tighten the definition of engaged to ensure only the most active subscribers receive emails, especially while recovering reputation. This aligns with advice on how to reduce your email bounce rate.
• Prioritize consistency: After the spike, maintaining a steady and predictable sending volume is key to reassuring ISPs and rebuilding a positive sender reputation.

Key opinions

• Throttling is key: Soft bounces, especially deferrals, often signify that ISPs are throttling your mail stream. This means they are delaying or temporarily rejecting your emails because your sender reputation has been affected.
• Reputation impact: A sudden spike in email volume, even to engaged users, can be enough to trigger ISPs to monitor your mail sources more closely. This can result in a lasting 'grey' reputation.
• Warning sign: High deferral rates are a warning that your mail stream reputation is borderline, potentially heading towards more serious issues like outright rejections or being marked as spam. It's an early indicator of a problem.
• ISP capacity vs. reputation: While throttling can sometimes be due to genuine capacity issues at the ISP, for larger providers, it's more frequently a sign that your emails are being deprioritized due to perceived lower importance or trustworthiness.

Key considerations

• Analyze ISP-specific deferrals: Dig deep into your logs to understand which specific ISPs are causing the most deferrals. This allows for targeted adjustments rather than broad changes. This is part of a larger troubleshooting process for spike-related bounces.
• Gradual sending rate reduction: For identified problematic ISPs, incrementally reduce your sending rate until the deferral issues diminish. This is a common practice in deliverability management.
• Long-term consistency: Beyond immediate fixes, commit to consistent sending volumes and patterns. This demonstrates stable behavior to ISPs and helps to slowly rebuild your email domain reputation.
• Proactive monitoring: Utilize tools like Google Postmaster Tools to monitor reputation metrics beyond just bounce rates, looking for signs of deprioritization.

Key findings

• Sender reputation: Documentation emphasizes that email volume spikes, even to engaged lists, can be perceived negatively by ISPs, leading to reputation damage and subsequent throttling (soft bounces).
• Soft bounce causes: Common causes of soft bounces include recipient mailbox being full, server issues at the recipient's end, or ISP throttling due to high volume, suspicious content, or a degraded sender reputation.
• Engagement measurement: While opening emails is a form of engagement, ISPs consider a broader range of signals including clicks, replies, and whether emails are moved out of spam folders. Relying solely on opens may not capture the full picture of engagement.
• Throttling as feedback: ISPs use throttling as a primary mechanism to manage incoming mail volume and provide implicit feedback on sender reputation. Persistent throttling signals a need for sender adjustments.

Key considerations

• Monitor ISP responses: Closely monitor bounce codes and responses from recipient ISPs. These provide specific reasons for deferrals and can guide remediation efforts. Understanding soft bounce retry policies can be helpful.
• Gradual volume adjustments: Instead of returning to previous high volumes immediately, gradually increase or decrease send rates based on deliverability feedback. Abrupt changes can trigger further throttling. Learn about reasonable soft bounce tolerance.
• List hygiene: Regularly clean your email list by removing unengaged or inactive subscribers to reduce the chance of hitting spam traps or being flagged by ISPs. Refer to Mailgun's insights on soft bounce prevention.
• Consistent sending patterns: Establish and adhere to consistent sending frequencies and volumes over time. This predictability helps ISPs accurately assess your sending behavior and rebuild trust.