Summary
A sudden increase in transactional email bounce rates can be triggered by a multitude of factors spanning from list quality to sender reputation and technical configurations. Sending to outdated or invalid email addresses, hitting spam traps, or being marked as spam by recipients can significantly damage sender reputation. List decay, stemming from inactive or non-existent addresses, and changes in spam filtering policies by ISPs also contribute. Being added to a blocklist prevents email delivery and results in bounces. Bounce types (hard, soft, block) reflect different underlying issues. Diagnosing the root cause necessitates examining actual rejection messages, analyzing SMTP error codes, and leveraging feedback loops from ESPs like Amazon SES, Google, and Microsoft. Maintaining list hygiene, implementing email authentication protocols (SPF, DKIM, DMARC), using email verification services, and regularly monitoring sender reputation are crucial preventive measures. Additionally, issues with specific email providers (e.g., Hotmail/Outlook, Comcast) may not be related to Google/Yahoo requirements.
Key findings
- Invalid Addresses: Outdated, invalid, or inactive email addresses are a major cause of increased bounce rates.
- Sender Reputation: Damaged sender reputation due to spam complaints or blocklisting significantly increases bounce rates.
- List Hygiene: Poorly maintained email lists with inactive subscribers and unvalidated addresses contribute to higher bounce rates.
- Bounce Types: Different bounce types (hard, soft, block) indicate various underlying issues, necessitating targeted diagnostic approaches.
- Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) can lead to increased bounce rates and emails being marked as spam.
- ISP Policies: Changes in spam filtering policies by ISPs can suddenly trigger an increase in bounce rates.
- Blocklisting: Being added to a blocklist prevents delivery and results in bounces.
- Rejection Messages: Analysing actual rejection messages including domain and IPs, is vital for understanding bounce origins and the specific reason codes
Key considerations
- Examine Rejection Messages: Carefully examine actual rejection messages, including the domain and IPs involved.
- Monitor SMTP Codes: Pay close attention to SMTP error codes provided by ESPs to identify the specific reasons for bounces.
- Maintain List Hygiene: Regularly clean your email list by removing inactive subscribers and validating email addresses.
- Verify Email Addresses: Use an email verification service to validate email addresses before sending campaigns.
- Implement Authentication: Implement SPF, DKIM, and DMARC to authenticate your emails and improve deliverability.
- Monitor Reputation: Use tools like Google Postmaster Tools to monitor your sender reputation and spam rates.
- Check Blocklists: Regularly check if sending IPs or domains are listed on common blocklists.
- Utilize ESP Support: Contact your ESP's support for assistance in analyzing rejection messages and diagnosing bounce issues.
- Differentiate Bounce Types: Differentiate between temporary failures, permanent failures, and block bounces for better problem identification
What email marketers say
10 marketer opinions
A sudden increase in transactional email bounce rates can stem from multiple factors. These include sending emails to outdated or invalid addresses, encountering spam traps, or recipients marking emails as spam, which negatively impacts sender reputation. Issues with email lists, such as decay or the presence of invalid addresses, contribute to higher bounce rates. Changes in spam filtering policies by ISPs and deliverability issues related to domain reputation can also cause sudden spikes. Identifying the type of bounce (hard or soft) is important, as hard bounces are permanent failures due to invalid addresses, while soft bounces are temporary. Diagnosing the root cause requires examining bounce codes, working with ESPs (Email Service Providers), and employing tools to monitor sender reputation and feedback loops. Implementing email authentication protocols (SPF, DKIM, DMARC), maintaining list hygiene, and using email verification services are crucial for prevention.
Key opinions
- Invalid Addresses: Sending to outdated, invalid, or inactive email addresses significantly increases bounce rates.
- Sender Reputation: Spam reports and being added to blocklists damage sender reputation, leading to higher bounce rates.
- List Hygiene: Poor list hygiene, including a lack of regular cleaning and validation, contributes to bounce issues.
- Bounce Types: Hard bounces are permanent failures, while soft bounces are temporary, indicating different underlying issues.
- Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) can lead to emails being marked as spam and bouncing.
- ISP Policies: Changes in spam filtering policies by ISPs can suddenly increase bounce rates.
Key considerations
- Monitor Bounce Codes: Regularly check and analyze bounce codes provided by your ESP to understand the specific reasons for bounces.
- Clean Email List: Implement a regular process to remove inactive subscribers and invalid email addresses from your list.
- Verify Addresses: Use an email verification service to validate email addresses before sending campaigns.
- Authenticate Emails: Implement SPF, DKIM, and DMARC to authenticate your emails and improve deliverability.
- Monitor Reputation: Use tools like Google Postmaster Tools to monitor your sender reputation and spam rates.
- ESP Collaboration: Work closely with your ESP to diagnose and address the root causes of increased bounce rates.
Marketer view
Email marketer from Mailjet explains that several factors can cause high bounce rates, including sending to outdated or invalid email addresses, spam traps, or when recipients mark emails as spam, damaging your sender reputation. The email might be flagged as spam if the content is suspicious.
20 Jan 2022 - Mailjet
Marketer view
Email marketer from Email Geeks shares that issues with Hotmail/Outlook or Comcast are not related to Google/Yahoo requirements.
17 Jun 2022 - Email Geeks
What the experts say
4 expert opinions
A sudden increase in transactional email bounce rates can often be attributed to blocklisting or delivery failures. It is crucial to examine the actual rejection messages, including the domain and IPs, to understand where the rejections are occurring. Rejection messages typically start with three digits, and ESP (Email Service Provider) support can be valuable in analyzing these messages. Bounce categories, such as temporary failures, permanent failures, and block bounces, should be differentiated to determine the root cause. Checking SMTP codes is necessary for diagnosis, and verifying if sending IPs or domains are listed on common blocklists is essential to identify blocklisting issues.
Key opinions
- Rejection Messages: Examining actual rejection messages, including domain and IPs, is vital for understanding bounce origins.
- SMTP Codes: Checking SMTP codes is necessary for correctly diagnosing the root cause of email bouncebacks
- Bounce Categories: Differentiating between temporary failures, permanent failures, and block bounces is essential for root cause analysis.
- Blocklisting: Sudden increases in bounce rates may be caused by being added to a blocklist.
Key considerations
- ESP Support: Contact ESP support for assistance in analyzing rejection messages and diagnosing bounce issues.
- Blocklist Checks: Regularly check if sending IPs or domains are listed on common blocklists.
Expert view
Expert from Email Geeks explains that rejection messages will start with three digits and suggests contacting the ESP's support for help, including providing sample rejection messages.
6 Jun 2022 - Email Geeks
Expert view
Expert from Email Geeks explains that to understand bounce rates, it's important to examine the actual rejection messages, including the domain and IPs being sent from and where they're being rejected.
13 Feb 2024 - Email Geeks
What the documentation says
5 technical articles
Understanding and addressing increased transactional email bounce rates involves utilizing various tools and mechanisms provided by email service providers and standards. Amazon SES offers SNS notifications, automatic suppression, and feedback loops. SMTP uses error codes, which are three-digit codes, to indicate the reason for the bounce. SparkPost classifies bounces based on these SMTP codes. Google Postmaster Tools helps monitor sender reputation, spam rates, and feedback loops. Outlook.com also provides feedback loop mechanisms and sender support. Analyzing the SMTP codes is essential for diagnosing the reason for the bounce.
Key findings
- SMTP Error Codes: SMTP utilizes three-digit error codes to specify the reason an email bounced, and analyzing these is crucial for diagnosis.
- Bounce Classification: Bounces can be classified into different types, such as hard, soft, or technical failures, based on SMTP response codes.
- Feedback Loops: Platforms like Amazon SES and Outlook.com provide feedback loops to help diagnose and address deliverability issues.
- Monitoring Tools: Google Postmaster Tools allows monitoring of sender reputation, spam rates, and feedback loop data to identify deliverability problems.
Key considerations
- Implement SNS Notifications: Use Amazon SES's SNS notifications to receive real-time bounce alerts.
- Analyze SMTP Codes: Pay close attention to SMTP error codes to understand the specific reasons for bounces.
- Monitor Reputation: Regularly monitor sender reputation using tools like Google Postmaster Tools.
- Utilize Feedback Loops: Leverage feedback loops provided by ESPs such as Outlook.com to address deliverability issues.
Technical article
Documentation from Microsoft explains that Outlook.com provides feedback loop mechanisms and sender support resources to help diagnose and address deliverability issues, including bounces, that can impact sender reputation and email placement.
25 Aug 2021 - Microsoft
Technical article
Documentation from SparkPost explains that bounces are classified based on SMTP response codes from the receiving mail server. This classification helps diagnose the reason for the bounce, categorizing them as hard, soft, or technical failures.
1 Sep 2022 - SparkPost
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