Summary
Soft bounces are temporary email delivery failures stemming from issues like full mailboxes, server downtime, or graylisting. Analyzing SMTP response codes and ESP bounce messages aids in diagnosis. Addressing these requires ensuring email content relevance, list hygiene, proper authentication (SPF, DKIM, DMARC), monitoring sender reputation, and maintaining consistent sending volumes. ESPs automatically retry delivery, but addressing underlying problems and adhering to provider guidelines is essential to prevent soft bounces from turning into hard bounces.
Key findings
- Temporary Nature: Soft bounces signify temporary email delivery failures (4xx SMTP codes).
- Variety of Causes: Common causes include full mailboxes, server downtime, graylisting, and DNS issues.
- Automatic Retries: ESPs like Amazon SES, Twilio SendGrid, and others automatically retry delivery.
- Impact of Reputation: Sender reputation significantly impacts soft bounce rates; poor reputation increases bounces.
Key considerations
- Analyze Bounce Data: Carefully review bounce messages from your ESP to pinpoint specific reasons for failures.
- List Hygiene: Regularly clean your email list to remove inactive or problematic addresses.
- Content Optimization: Ensure your email content is relevant, engaging, and doesn't trigger spam filters.
- Authentication Protocols: Implement SPF, DKIM, and DMARC to authenticate your emails and improve deliverability.
- Sending Infrastructure: Properly configure your sending infrastructure to prevent server-side delivery issues.
- Sending Volume: Maintain consistent and appropriate sending volumes to avoid being blacklisted.
- Address Acquisition: Consider the age and acquisition method of email addresses; avoid sending to old or unengaged addresses.
What email marketers say
9 marketer opinions
Soft bounces indicate temporary email delivery issues, such as full mailboxes, server downtime, or graylisting. Resolving these involves identifying the bounce classification and origin, cleaning email lists, improving content relevance, ensuring proper email authentication (SPF, DKIM, DMARC), and monitoring sender reputation. Sending to engaged recipients and resolving immediate issues contribute to minimizing soft bounces.
Key opinions
- Temporary Issues: Soft bounces are typically caused by temporary issues like full mailboxes, server problems, or graylisting.
- List Hygiene: Maintaining a clean email list is crucial to reducing soft bounces.
- Content Relevance: Relevant email content helps avoid triggering spam filters.
- Authentication: Proper email authentication (SPF, DKIM, DMARC) improves deliverability.
- Sender Reputation: Monitoring and maintaining a good sender reputation is essential.
Key considerations
- Bounce Classification: Identify the specific classification and providers of soft bounces to diagnose the root cause.
- Sending Volume: Maintain a consistent sending volume to avoid triggering graylisting.
- Engagement: Focus on sending emails to engaged recipients to improve deliverability.
- Email Size: Avoid sending overly large emails, as they can contribute to soft bounces.
- Monitoring: Continuously monitor bounce rates and take prompt action based on feedback loops.
Marketer view
Email marketer from StackExchange explains that soft bounces mean a temporary issue occurred, such as a server being unreachable or a quota being exceeded. Resolving the immediate issues and following email best practices, like authenticating your domain, is recommended.
17 Oct 2022 - StackExchange
Marketer view
Email marketer from Reddit shares that soft bounces are often due to temporary problems like the recipient's server being down or their mailbox being full. To fix it, ensure your list is clean and that you are not sending overly large emails, and monitor your sending reputation.
31 Dec 2023 - Reddit
What the experts say
4 expert opinions
Soft bounces are often temporary failures caused by various issues, including full mailboxes, server unavailability, or graylisting. Analyzing bounce messages from your ESP is crucial. Addressing infrastructure configuration, content triggering spam filters, sending frequency, recipient engagement, and implementing proper authentication methods (SPF, DKIM, DMARC) can help resolve soft bounces.
Key opinions
- Temporary Failures: Soft bounces are primarily caused by temporary issues such as full mailboxes or server unavailability.
- Graylisting: Graylisting, where servers temporarily reject mail from unknown senders, is a common cause of soft bounces.
- Recipient Engagement: Sending to engaged recipients helps to minimize soft bounces.
- Authentication: Proper authentication (SPF, DKIM, DMARC) reduces graylisting and improves deliverability.
Key considerations
- Bounce Analysis: Review bounce messages from your ESP to understand the specific reasons for soft bounces.
- Infrastructure Configuration: Ensure your sending infrastructure is properly configured to minimize delivery issues.
- Content: Ensure your email content is not triggering spam filters.
- Sending Practices: Maintain a consistent sending volume to avoid being blacklisted.
- Address Age & Acquisition: Consider how old the addresses are, how frequently you send, and how they were acquired.
Expert view
Expert from Email Geeks explains that there are many reasons why email might temporarily fail to deliver. You should review messages returned by the sending server from your ESP and analyze the reason for the soft bounce.
13 Jan 2024 - Email Geeks
Expert view
Expert from Word to the Wise explains that graylisting is a common cause of soft bounces, where a receiving server temporarily rejects mail from an unknown sender. It recommends proper authentication (SPF, DKIM, DMARC), maintaining a consistent sending volume, and ensuring your IP address is not blacklisted.
7 Mar 2025 - Word to the Wise
What the documentation says
5 technical articles
Soft bounces, identified by 4xx SMTP response codes, are temporary email delivery failures often caused by issues like full mailboxes, DNS problems, or general server unavailability. Email service providers like Amazon SES, Exchange Online, SparkPost, and Twilio SendGrid automatically retry delivery for a defined period. Addressing underlying issues, monitoring bounce notifications, ensuring email relevance, keeping lists updated, and adhering to provider guidelines are crucial for resolving persistent soft bounces and preventing them from becoming hard bounces.
Key findings
- Temporary Failure: Soft bounces represent temporary delivery failures, as indicated by 4xx SMTP response codes.
- Automatic Retries: ESPs like Amazon SES, Exchange Online, SparkPost, and Twilio SendGrid automatically retry delivery for a certain period.
- Potential for Hard Bounce: If the issue persists, a soft bounce can eventually turn into a hard bounce.
Key considerations
- Underlying Issues: Address underlying issues like content problems or sender reputation to reduce soft bounces.
- Bounce Monitoring: Monitor bounce notifications to identify and address issues promptly.
- List Maintenance: Keep email lists updated and send relevant email to minimize bounces.
- Provider Guidelines: Ensure your email practices comply with the guidelines of your email service provider (e.g., AWS).
- SMTP Codes: Understanding SMTP response codes can aid in diagnosing email delivery issues.
Technical article
Documentation from Twilio SendGrid describes that soft bounces are temporary delivery failures and they will automatically attempt to resend for up to 72 hours. However, if the email isn't sent it may become a permanent bounce. To avoid this from happening, be sure to send relevant email and keep lists updated.
31 May 2022 - Twilio SendGrid
Technical article
Documentation from Amazon Web Services explains that Amazon SES handles soft bounces by attempting redelivery for a certain period. A soft bounce typically indicates a temporary issue, such as the recipient's mailbox being full. If the issue persists, the soft bounce might eventually turn into a hard bounce. Monitor bounce notifications and ensure your email practices comply with AWS guidelines.
22 Sep 2024 - Amazon Web Services
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