Summary
Gmail delivery failures between Gmail addresses are multifaceted, stemming from sender-side issues, Gmail's internal filtering mechanisms, and recipient-side configurations. Key factors include exceeding Gmail's daily sending limits, triggering aggressive spam filters with problematic email content, poor sender/domain reputation due to spam activity or complaints, inadequate sender authentication (SPF, DKIM, DMARC), internal blocklists, SMTP errors, restrictive Google Groups settings, and the need to warm up new Gmail accounts. Troubleshooting involves checking authentication records, monitoring reputation, practicing list hygiene, and reviewing email content.
Key findings
- Sending Limits: Gmail has daily sending limits; exceeding these prevents email delivery.
- Spam Filters: Aggressive spam filters may incorrectly flag legitimate emails with promotional content.
- Reputation Issues: Poor IP/domain/sender reputation, resulting from spam activity/complaints, leads to blocking or filtering.
- Authentication Failures: Incorrect/missing SPF, DKIM, DMARC records prevent sender verification and cause rejections.
- Internal Blocklists: Gmail uses internal blocklists/reputation systems that may not be publicly accessible.
- Content Triggers: Email content with spam-like keywords/links triggers spam filters.
- Group Settings: Recipient's Google Groups settings may be too restrictive.
- Account Warmup: New Gmail accounts need a 'warm-up' period before sending emails.
- SMTP Errors: SMTP errors during transmission can cause email delivery to fail without generating a bounce message.
Key considerations
- MX Lookup: Perform an MX lookup on the sender's domain to identify the email provider.
- Authentication Checks: Ensure proper configuration and validation of SPF, DKIM, and DMARC records.
- Reputation Monitoring: Monitor sender/domain reputation using Google Postmaster Tools.
- List Hygiene: Practice good list hygiene by removing unengaged recipients.
- Content Review: Review email content to avoid spam-triggering keywords/links.
- Account Warmup: Gradually warm up new accounts by sending to engaged recipients first.
- Complaint Handling: Monitor and address spam complaints to improve sender reputation.
- Google Groups Settings: Consider the recipient's Google Groups configuration.
- SMTP Error Handling: Implement robust SMTP error handling to identify and resolve transmission issues.
What email marketers say
11 marketer opinions
Gmail addresses not sending to other Gmail addresses can stem from various issues. These include exceeding Gmail's daily sending limits, aggressive spam filtering, poor IP or domain reputation, internal blocklists, problematic email content triggering spam filters, DMARC policy failures, low sender reputation, recipient's Google Groups settings, and the need for new accounts to 'warm up'. Troubleshooting often requires checking sender authentication (SPF, DKIM, DMARC), monitoring complaint rates, and ensuring proper list hygiene.
Key opinions
- Sending Limits: Gmail has daily sending limits that, when exceeded, prevent email delivery.
- Spam Filters: Gmail's aggressive spam filters can incorrectly flag legitimate emails, especially with promotional content or certain keywords.
- Reputation: Poor IP or domain reputation due to previous spam activity can cause Gmail to block or filter emails.
- Authentication: DMARC policy failures (due to SPF or DKIM issues) can lead to email rejections.
- Sender Reputation: A low sender reputation causes Gmail to view the sender as untrustworthy, leading to filtering.
- Content Triggers: Email content resembling spam or phishing attempts can trigger Gmail's filters.
Key considerations
- MX Lookup: Perform an MX lookup on the sender's domain to identify the email provider.
- Check Authentication: Ensure SPF, DKIM, and DMARC records are correctly configured to authenticate your emails.
- Monitor Reputation: Regularly monitor your sender reputation and domain reputation using tools like Google Postmaster Tools.
- List Hygiene: Maintain good list hygiene by removing unengaged recipients and minimizing bounce rates.
- Content Review: Review email content to avoid using spam-triggering words or suspicious links.
- Account Warm-up: Gradually warm up new Gmail accounts by sending emails to engaged recipients first.
- Google Groups: Consider the recipient's Google Groups settings, as these may be too strict.
Marketer view
Email marketer from Google Support explains that Gmail accounts have daily sending limits, and exceeding those limits can cause emails to be undelivered. The limits vary based on account type.
7 Jan 2024 - Google Support
Marketer view
Email marketer from Reddit user shares that Gmail's spam filters are aggressive and can sometimes incorrectly flag legitimate emails as spam, especially if the content is promotional or contains certain keywords.
5 May 2025 - Reddit
What the experts say
4 expert opinions
Gmail delivery issues between Gmail addresses are often linked to sender reputation, which is affected by domain history, list hygiene, authentication practices, and user complaint rates. A new or spam-tainted domain increases the likelihood of filtering, as does sending to unengaged addresses. Inadequate SPF, DKIM, and DMARC records hinder sender verification, leading to potential blocks. High complaint rates from Gmail users significantly damage sender reputation and increase the chances of emails being filtered.
Key opinions
- Domain Reputation: Gmail filtering heavily relies on the sending domain's reputation; a new or problematic history increases filtering.
- List Hygiene: Poor list hygiene results in higher bounce rates and spam complaints, harming sender reputation.
- Sender Authentication: Inadequate SPF, DKIM, and DMARC records prevent sender verification and lead to possible blocks.
- Complaint Rates: High complaint rates significantly damage sender reputation, increasing filtering likelihood.
Key considerations
- Domain History Review: Check the history and reputation of your sending domain to identify potential issues.
- Implement List Cleaning: Regularly clean your email list by removing inactive or unengaged recipients.
- Verify Authentication Setup: Ensure that SPF, DKIM, and DMARC records are correctly configured and validated.
- Monitor Complaint Feedback: Actively monitor and address spam complaints to improve sender reputation.
Expert view
Expert from Spam Resource explains that Gmail's filtering can be heavily influenced by the sending domain's reputation. If the domain is new or has a history of sending spam, Gmail is more likely to block or filter emails, even if they are legitimate.
6 May 2024 - Spam Resource
Expert view
Expert from Spam Resource explains that poor list hygiene, such as sending to old or unengaged email addresses, can lead to higher bounce rates and spam complaints, which can negatively impact sender reputation and cause Gmail to block or filter emails.
7 Jan 2025 - Spam Resource
What the documentation says
4 technical articles
Gmail delivery failures between Gmail addresses can be attributed to incorrect or missing SPF records preventing sender authentication, a low domain reputation stemming from spam rates and user complaints, SMTP errors occurring during transmission without bounce messages, or missing/invalid DKIM signatures causing distrust. Proper email authentication and a healthy domain reputation are crucial for ensuring deliverability.
Key findings
- SPF Records: Incorrect or missing SPF records cause Gmail to reject emails due to failed sender authentication.
- Domain Reputation: Low domain reputation, influenced by spam rates and user complaints, leads to email filtering.
- SMTP Errors: SMTP errors during transmission can prevent delivery without generating bounce messages.
- DKIM Signatures: Missing or invalid DKIM signatures cause Gmail to distrust emails, leading to filtering.
Key considerations
- SPF Configuration: Verify and correct SPF records to ensure proper sender authentication.
- Reputation Management: Monitor and improve domain reputation by minimizing spam rates and user complaints.
- Error Handling: Implement robust SMTP error handling to identify and resolve transmission issues.
- DKIM Implementation: Ensure valid DKIM signatures are implemented to enhance email trustworthiness.
Technical article
Documentation from RFC Standards explains that SMTP errors during the email transmission process (e.g., temporary or permanent failures) can prevent delivery, even if no bounce message is received by the original sender.
10 Jan 2025 - RFC Editor
Technical article
Documentation from DKIM.org explains that a missing or invalid DKIM signature can cause Gmail to distrust the email and potentially filter it.
23 Jul 2022 - DKIM.org
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