Summary
Emails being marked as 'dangerous' in Gmail when using microdata markup results from a complex interplay of factors. While the markup itself may not always be the direct cause, its incorrect implementation, misleading content, or its association with other deliverability issues triggers Gmail's spam filters. Key issues include poor sender reputation, lack of email authentication (SPF, DKIM, DMARC), low engagement rates, and content that resembles phishing attempts. Proper implementation according to Google's guidelines, proper DMARC policy, validation of markup, and maintaining a clean email list are essential to prevent emails from being flagged.
Key findings
- Markup Implementation: Incorrect or invalid microdata markup can trigger Gmail's spam filters.
- Email Content: Misleading content, spam trigger words, or suspicious URLs associated with the markup contribute to the issue; content may also resemble phishing.
- Sender Reputation: Poor sender reputation or a new domain increases the likelihood of emails being flagged.
- Email Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) makes emails appear suspicious.
- Engagement Metrics: Low engagement rates (low open rates, click-through rates) can lead to Gmail filtering emails.
- Registration: Gmail registration/validation of markup usage may be required.
- DMARC Policy: A failing DMARC policy can lead to Gmail distrust, especially with new markup.
Key considerations
- Validate Markup: Validate microdata markup using tools like Google's Rich Results Test.
- Review Content: Ensure the content associated with the markup is not misleading, spammy, or similar to phishing attempts.
- Implement Authentication: Properly configure SPF, DKIM, and DMARC for the sending domain.
- Monitor Deliverability: Monitor email deliverability and engagement metrics after implementing microdata markup.
- Clean Email List: Maintain a clean and engaged email list.
- Gradual Rollout: Consider a gradual rollout of the microdata markup to observe its impact.
- Google Guidelines: Adhere to Google's specific implementation guidelines for schema markup.
- Schema.org Standards: Use correct vocabulary and syntax as defined by schema.org.
- MIME Types: Use the correct MIME types and encoding for email content, including markup.
What email marketers say
11 marketer opinions
Emails marked as 'dangerous' in Gmail when using microdata markup can stem from various factors, not solely the markup itself. Incorrect implementation of markup, misleading or incorrect data, and sudden changes to email content can trigger spam filters. External factors such as poor sender reputation, lack of email authentication (SPF, DKIM, DMARC), spam trigger words, suspicious URLs, and low engagement rates also play a significant role.
Key opinions
- Markup Implementation: Incorrect or invalid microdata markup can trigger Gmail's spam filters.
- Email Content: Misleading content, spam trigger words, or suspicious URLs associated with the markup contribute to the issue.
- Sender Reputation: Poor sender reputation or a new domain increases the likelihood of emails being flagged.
- Email Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) makes emails appear suspicious.
- Engagement Metrics: Low engagement rates (low open rates, click-through rates) can lead to Gmail filtering emails.
- Registration: Gmail registration/validation of markup usage may be required.
Key considerations
- Validate Markup: Validate microdata markup using tools like Google's Rich Results Test.
- Review Content: Ensure the content associated with the markup is not misleading or spammy.
- Implement Authentication: Properly configure SPF, DKIM, and DMARC for the sending domain.
- Monitor Deliverability: Monitor email deliverability and engagement metrics after implementing microdata markup.
- Clean Email List: Maintain a clean and engaged email list.
- Gradual Rollout: Consider a gradual rollout of the microdata markup to observe its impact.
Marketer view
Email marketer from HubSpot shares that building and maintaining a good domain reputation is vital. If your domain is relatively new or has a poor reputation, Gmail might be more likely to flag emails, especially those containing advanced markup.
13 Aug 2023 - HubSpot
Marketer view
Email marketer from SendGrid explains that proper email authentication (SPF, DKIM, DMARC) is crucial for establishing sender credibility. If the domain isn't properly authenticated, Gmail might view emails with suspicion, especially when combined with new or unusual markup.
1 Jan 2023 - SendGrid
What the experts say
3 expert opinions
Emails with microdata markup may be marked as dangerous in Gmail due to several interconnected factors. The email content may resemble phishing attempts, triggering spam filters. Poor IP or domain reputation, inadequate email authentication (SPF, DKIM, DMARC), and improper DMARC implementation can also cause Gmail to distrust the emails, particularly when combined with new or unfamiliar markup. Testing with a newly created Gmail account and ensuring correct DMARC policy are vital for troubleshooting.
Key opinions
- Phishing Resemblance: Email content resembling phishing attempts can trigger Gmail's spam filters.
- Poor Reputation: Poor IP or domain reputation increases the likelihood of emails being flagged.
- Authentication Issues: Inadequate email authentication (SPF, DKIM, DMARC) makes emails appear suspicious.
- DMARC Implementation: Improper DMARC implementation can lead to Gmail distrust, especially with new markup.
- Registration: Gmail registration/validation of markup usage may be required.
Key considerations
- Content Review: Review email content to ensure it does not resemble phishing attempts.
- Reputation Monitoring: Monitor IP and domain reputation to identify and address any issues.
- Authentication Setup: Properly configure SPF, DKIM, and DMARC for the sending domain.
- DMARC Validation: Ensure DMARC policy is correctly implemented and not failing.
- Testing: Test email deliverability with a newly created Gmail account to isolate the issue.
Expert view
Expert from Word to the Wise shares that proper DMARC implementation is essential for Gmail to trust the emails, especially with the presence of microdata. A failing DMARC policy can lead to emails being marked as dangerous or spam, particularly when combined with unusual content or markup.
1 Oct 2023 - Word to the Wise
Expert view
Expert from Email Geeks suggests that the issue might be related to the email content resembling phishing. They advise testing with a newly created Gmail account to confirm the issue and narrow down the cause. It is also suggested that not registering with Google could be an issue.
22 Jan 2023 - Email Geeks
What the documentation says
5 technical articles
Emails with microdata markup may be marked as dangerous in Gmail due to violations of specific implementation guidelines. Google Developers, schema.org, and Litmus emphasize proper syntax, vocabulary, and adherence to defined structures. Poor implementation impacts sender reputation, authentication (SPF, DKIM, DMARC), and engagement metrics. Microsoft offers general guidelines for senders, and RFC highlights the importance of MIME types. Proper implementation is essential for email clients to correctly interpret the content, avoiding rendering issues and potential spam flags.
Key findings
- Implementation Guidelines: Failing to meet Google's guidelines for schema markup can lead to deliverability penalties.
- Correct Syntax/Vocabulary: Adhering to specified vocabulary and syntax in schema markup is crucial.
- Sender Reputation/Authentication: Improper markup implementation negatively impacts sender reputation and authentication factors.
- Proper MIME types: Incorrect MIME types can lead to rendering issues and spam flags.
Key considerations
- Google Guidelines: Adhere to Google's specific implementation guidelines for schema markup.
- Schema.org Standards: Use correct vocabulary and syntax as defined by schema.org.
- Email Protocols: Properly configured SPF, DKIM and DMARC is key to ensuring reputation and deliverability
- MIME Types: Use the correct MIME types and encoding for email content, including markup.
Technical article
Documentation from Google Developers explains that Google has specific guidelines for implementing schema markup, and failing to meet these guidelines can lead to penalties, including deliverability issues.
21 May 2023 - Google Developers
Technical article
Documentation from schema.org details the correct way to implement schema markup, emphasizing the importance of adhering to the specified vocabulary and syntax to avoid issues with email clients.
2 Jun 2025 - schema.org
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