Summary
Valid Gmail and Yahoo email addresses may bounce after website verification due to a multitude of factors. These include temporary server issues, full mailboxes, spam filtering by Gmail and Yahoo, greylisting, poor sender reputation, and problems stemming from email verification techniques themselves. Getting the actual rejection messages from the ESP is crucial for accurate diagnosis. Data capture errors (like spaces) and authentication issues also play a significant role. Addressing this requires a multi-faceted approach: analyzing bounce codes, improving sender reputation through best practices and proper authentication (SPF, DKIM, DMARC), regular list hygiene, utilizing deliverability testing tools, investigating data and code errors, opening a ticket with the ESP (and potentially escalating), and evaluating the impact and methods of your email verification service.
Key findings
- Multiple Bounce Causes: Bounces are rarely due to a single cause; consider various factors.
- ESP Summary Inaccuracy: ESP bounce summaries are often insufficient; always get the actual rejection message.
- Data Capture Problems: Errors in data capture (e.g., spaces) can lead to bounces.
- Verification Limitations: Email verification doesn't guarantee deliverability.
- Verification Side Effects: Some verification methods can negatively impact deliverability.
- Temporary Issues: Greylisting and temporary server issues can cause temporary bounces.
- Sender Reputation Matters: Sender reputation is crucial for deliverability, even for valid addresses.
- Authentication is Key: Proper email authentication (SPF, DKIM, DMARC) is vital.
- Analyze Bounce Codes: Analyze the specific bounce codes provided by ESPs
- List Hygiene is important: Regularly prune your email lists
Key considerations
- Examine Rejection Messages: Prioritize examining full rejection messages from your ESP over summaries.
- Review Data Capture: Thoroughly audit data capture processes for errors.
- Evaluate Verification Services: Carefully assess the impact and methods of your email verification service and consider alternative options.
- Implement Email Warmup: Warmup your sending IP's to improve reputation
- Address Authentication: Always configure SPF, DKIM and DMARC for all email sends.
- Consider temporary issues: Be aware that greylisting and temporary unavailability might resolve after some time.
- ESP Troubleshooting: Escalate your ESP support ticket to make sure it receives proper attention.
- Monitor Sending Reputation: Routinely monitor your email reputation with a tool like GlockApps or similar
- Test Email Deliverability: Test email sends to different providers and check placement in inbox versus spam.
What email marketers say
12 marketer opinions
Valid Gmail and Yahoo email addresses can bounce after website verification due to various reasons, including temporary server issues, full inboxes, aggressive spam filters, and greylisting. Email verification confirms address existence but not guaranteed deliverability. Sender reputation and email authentication (SPF, DKIM, DMARC) are key factors. It's crucial to analyze bounce codes, maintain list hygiene (removing inactive addresses), and consider testing deliverability with specialized tools. Issues can also stem from verification services themselves, and temporary deliverability problems.
Key opinions
- Temporary Issues: Temporary server issues, full mailboxes, or spam filters can cause bounces even for valid addresses.
- Verification Limitations: Email verification confirms the existence of an address but doesn't guarantee deliverability.
- Sender Reputation: Poor sender reputation can lead to bounces, even with valid email addresses.
- Authentication Importance: Proper email authentication (SPF, DKIM, DMARC) improves deliverability and reduces bounces.
- Bounce Code Analysis: Analyzing bounce codes is crucial to understand the specific reasons for email bounces.
- List Hygiene: Regularly cleaning email lists to remove inactive or abandoned addresses is essential.
- Testing Tools: Using email testing tools can help identify deliverability issues before sending to the entire list.
- ESP Troubleshooting: Opening a ticket with the ESP and escalating if necessary is vital for resolving bounce issues.
- Email Validation Service Issues: Some Email Validation Services can negatively impact deliverability.
Key considerations
- Investigate Bounce Codes: Carefully examine bounce codes provided by your ESP to pinpoint the exact cause of the delivery failure.
- Improve Sender Reputation: Focus on building and maintaining a good sender reputation by following email best practices.
- Implement Authentication: Ensure that SPF, DKIM, and DMARC are properly configured for your sending domain.
- Clean Email Lists: Regularly remove inactive, invalid, or unengaged email addresses from your lists.
- Test Deliverability: Utilize email testing tools to assess deliverability to different providers (Gmail, Yahoo, etc.) before large-scale sends.
- Review Verification Process: Evaluate the effectiveness of your email verification process and consider alternative methods if necessary.
- Email Warmup Process: Utilize an email warmup process to help build a send reputation.
Marketer view
Email marketer from Email Geeks suggests testing the theory of emails bouncing immediately after signup by delaying the welcome email by a minute or two.
5 Apr 2022 - Email Geeks
Marketer view
Email marketer from MailerCheck Blog explains that valid emails can bounce due to temporary server problems, spam filters, or full mailboxes. They stress the importance of analyzing bounce codes to understand the reason for the bounce.
14 May 2024 - MailerCheck Blog
What the experts say
5 expert opinions
Valid Gmail and Yahoo addresses might bounce post-verification due to ESP data summaries masking key details (requiring actual rejection messages for clarity), data capture errors like leading/trailing spaces, or greylisting causing temporary unavailability. Investigate code with a hex dump and consider verification services' problematic impact on deliverability. Contact Sendgrid to further clarify the issue.
Key opinions
- ESP Data Limitations: ESP summaries of bounce reasons are often insufficient; obtain the actual rejection message for detailed information.
- Data Capture Issues: Bad data capture, such as leading or trailing spaces in email addresses, can cause bounces.
- Greylisting Effects: Temporary deliverability issues, like greylisting, can cause initial bounces even with valid addresses.
- Problematic Verification Services: Some email verification techniques can negatively impact deliverability, leading to bounces.
Key considerations
- Review Rejection Messages: Prioritize obtaining and analyzing the complete rejection messages from your ESP to understand the bounce reason fully.
- Examine Data Capture Methods: Scrutinize your data capture process for potential errors, such as leading/trailing spaces or invalid characters.
- Investigate Code: Involve developers to examine the data and code for potential issues, potentially using a hex dump.
- Consider Greylisting: Be aware that temporary issues like greylisting can cause initial bounces that resolve on subsequent attempts.
- Evaluate Verification Services: Assess the impact of your chosen email verification service on your deliverability and consider alternatives if necessary.
- Contact Sendgrid: Open a ticket with Sendgrid and provide them with any data that you have to ensure that they investigate correctly.
Expert view
Expert from Word to the Wise explains that temporary deliverability issues can arise even with valid email addresses due to greylisting or temporary server unavailability at Gmail or Yahoo. These can cause initial bounces, but subsequent attempts may succeed.
24 Feb 2022 - Word to the Wise
Expert view
Expert from Email Geeks suggests that one cause of bounces could be bad data capture, such as a leading or trailing space in the email address.
22 May 2022 - Email Geeks
What the documentation says
4 technical articles
Valid email addresses can bounce due to temporary server unavailability, full mailboxes, spam filtering, low sender reputation, or suspicious content. SMTP servers use reply codes, with 5xx indicating permanent and 4xx temporary failures. Analyze bounce messages and NDRs for specific error codes to diagnose the issue. Following best practices for authentication and content is crucial to avoid bounces.
Key findings
- Temporary Unavailability: Recipient server issues can cause bounces.
- Mailbox Issues: Full mailboxes result in bounces.
- Spam Policies: Spam filters block delivery.
- Reply Codes: SMTP servers use reply codes to signal outcomes.
- NDR Analysis: NDRs (bounce messages) contain information.
- Sender Reputation: Low reputation impacts delivery.
Key considerations
- Check Bounce Messages: Always analyze bounce messages and NDRs.
- Monitor Server Availability: Be aware of possible server issues on the recipients end.
- Content: Ensure appropriate email content and avoid spam words.
- Improve Reputation: Focus on a positive email sending reputation
- Authentication: Ensure to authenticate using SPF, DKIM, and DMARC
Technical article
Documentation from Google Support explains that bounced emails can occur even for valid addresses if the recipient's server is temporarily unavailable, the mailbox is full, or the email is blocked due to spam policies. They recommend checking the bounce message for specific error codes.
7 May 2025 - Google Support
Technical article
Documentation from Microsoft Support explains that Non-Delivery Reports (NDRs) or bounce messages provide information about why an email could not be delivered. Analyzing the error code in the NDR can help identify the cause of the bounce, such as a full mailbox or a spam filter.
28 Mar 2025 - Microsoft Support
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