How to prevent Gmail from marking emails as phishing due to linked login pages?
Matthew Whittaker
Co-founder & CTO, Suped
Published 10 Jul 2025
Updated 14 Aug 2025
10 min read
Summary
Emails linking to login pages can sometimes be incorrectly flagged as phishing by Gmail, even when they are legitimate. This often occurs because the linked page, or the email itself, inadvertently mimics patterns associated with malicious attempts. Common triggers include the absence of HTTPS (SSL) on the login page, minimal content on the landing page, or a domain that, despite not being on public blacklists, is viewed with suspicion by Gmail's advanced heuristics. Understanding these factors and implementing best practices is crucial for ensuring your emails reach the inbox safely.
Key findings
SSL/HTTPS is critical: Gmail is highly sensitive to the use of HTTPS on linked login pages. The absence of a secure connection is a major red flag, often leading to phishing warnings.
Page content matters: Login pages with very sparse content—just input fields and nothing else—can appear suspicious, as this design is frequently used by phishing sites. Adding descriptive text and branding can help.
Beyond blacklists: A domain might not be listed on public blacklists (or blocklists), yet Gmail's internal reputation systems and advanced phishing detection algorithms can still flag it as insecure based on various behavioral and technical signals.
Mimicking phishing patterns: Gmail's filters are designed to recognize patterns commonly found in phishing attacks, including deceptive links, unusual domain names, and the overall context of the email and its linked content.
Domain reputation: Your overall domain reputation with Gmail plays a significant role. A low reputation increases the chance of legitimate emails being flagged.
Key considerations
Secure all login pages: Ensure that any page linked from your emails that requires user credentials uses HTTPS with a valid SSL certificate. This is non-negotiable for trust and security.
Enrich linked page content: Beyond just login fields, add sufficient explanatory text, branding, and clear navigation to your login pages. This helps distinguish them from malicious phishing sites.
Monitor domain health: Use Google Postmaster Tools to track your domain's reputation, spam rates, and other deliverability metrics. While it may not directly show phishing flags, it provides insights into overall domain trust.
Review email content and links: Scrutinize your email body and all linked URLs for anything that could appear deceptive or suspicious. Ensure brand consistency across emails and linked pages. Fastmail's help article on phishing and login page links provides a good overview.
What email marketers say
Email marketers frequently encounter the challenge of legitimate emails being flagged as phishing, especially when they contain links to login pages. Their discussions often revolve around practical, trial-and-error solutions, identifying common pitfalls like insecure linked pages and the impact of email structure. They often emphasize immediate checks and adjustments to email content and linked domains to quickly resolve these critical deliverability issues. Their collective experience highlights the need for constant vigilance and adaptability.
Key opinions
Linked page security is paramount: Marketers frequently point to the security (or lack thereof) of the linked login page as the primary cause of phishing flags, particularly the absence of SSL.
Content simplicity can be suspicious: A login page consisting only of input boxes, with no other content, is often seen as a significant trigger for phishing warnings, mimicking typical scam sites.
Testing isolating variables: A common suggestion is to remove the suspect link entirely and re-test, confirming if the linked domain is indeed the root cause of the phishing alert.
Beyond public blocklists: Marketers note that a domain can be flagged as insecure by Gmail even if it doesn't appear on any general blacklist or blocklist.
Google Search Console for insights: Some marketers suggest checking Google Search Console for any security alerts regarding the linked domain, as it provides Google's perspective on the site's safety.
Key considerations
Implement SSL/HTTPS immediately: The very first step should be to secure any linked login page with an SSL certificate. This is a fundamental security requirement for Gmail and other providers.
Add contextual content to login pages: Beyond just the login form, ensure your linked pages include descriptive text, branding, and clear information to establish legitimacy and reduce suspicion.
Assess email structure: Consider if your email’s format or inclusion of certain elements, such as PDFs, could be inadvertently triggering phishing filters. Simplicity and clarity often lead to better inbox placement.
Continuous monitoring: Regularly check all linked domains for security issues and monitor your email deliverability. Solutions like WP Mail SMTP provide useful guidance on how to fix Gmail blocking emails, emphasizing authentication and security.
Understand Gmail's alerts: Familiarize yourself with the nuances of Gmail’s 'This message seems dangerous' alert to better diagnose issues related to phishing flags.
Marketer view
Marketer from Email Geeks inquired about email structure. They asked if the email included elements like PDFs, suggesting that the overall composition of the message plays a role in how Gmail assesses it for phishing. This indicates that Gmail's algorithms scrutinize not just links, but the entire content and attachment profile.They implied that complex or unusual email structures might inadvertently trigger suspicion, even if the content itself is benign. This highlights a need for marketers to consider how their email's design might be perceived by automated phishing detection systems, beyond just the presence of external links.
29 Aug 2019 - Email Geeks
Marketer view
Marketer from Email Geeks shared observations on domain recognition. They noted that a domain might not appear on public blacklists yet still be recognized as insecure by Gmail, especially if it lacks proper security measures like SSL. This points to Gmail's use of internal, proprietary blocklists and advanced heuristics that go beyond publicly available data.This experience underscores that a seemingly "clean" domain, according to general blacklist checks, can still face deliverability challenges if it doesn't meet specific ISP security standards. Senders need to look beyond generic checks and understand the nuanced requirements of major email providers.
29 Aug 2019 - Email Geeks
What the experts say
Email deliverability experts provide deeper insights into Gmail's sophisticated phishing detection mechanisms. They consistently emphasize that the technical configuration and content of linked pages, particularly login forms, are meticulously scrutinized. The consensus is that any element mimicking known phishing tactics—such as a lack of encryption or sparse, generic content—will trigger alarms. Experts also highlight that while public blocklists might not show an issue, Gmail's internal reputation systems are highly sensitive to these subtle yet critical indicators of potential malicious activity. Adherence to web security standards is often cited as a prerequisite for email deliverability.
Key opinions
SSL is non-negotiable: Experts universally agree that the absence of HTTPS (SSL) on a login page is a primary trigger for Gmail's phishing warnings, making it an absolute minimum requirement.
Content and appearance matter: A login page with only input fields and no descriptive text or branding looks highly suspicious to automated filters, mirroring common phishing site designs.
Google's sophisticated detection: Gmail's algorithms are advanced enough to recognize not just malicious domains, but also the visual and structural patterns characteristic of phishing attempts, regardless of external blocklist status.
Comprehensive domain health checks: Beyond email metrics, checking tools like Google Search Console for broader domain security alerts is crucial, as issues there can impact email trust.
Proactive security is key: Maintaining a high level of security across all linked web properties is essential, as even a single insecure link can jeopardize the deliverability of an entire email campaign.
Key considerations
Prioritize HTTPS implementation: Immediate implementation of HTTPS on all linked login pages is the most impactful step you can take to prevent phishing warnings.
Enhance linked page legitimacy: Ensure that your login pages are not just functional but also visually legitimate, with adequate content and clear branding that aligns with your email sender identity.
Understand Gmail's heuristics: Recognize that Gmail's detection goes beyond simple blocklist lookups. It analyzes context, content, and security features to determine trustworthiness. The article on what happens if you click a phishing link underscores the risks Gmail is trying to mitigate.
Address domain reputation holistically: If your Gmail domain reputation is low, this could amplify phishing warnings. Work on improving it through consistent good sending practices and authentication.
Review email for phishing triggers: Conduct thorough reviews of your email content and linked URLs for any elements that might inadvertently trigger a phishing warning, ensuring they clearly represent your brand and intent.
Expert view
Expert from Email Geeks precisely identified a common trigger. They pointed out that a non-HTTPS website featuring only a username and password input box is a classic signature that Gmail’s phishing detection systems look for. This minimalist, insecure setup strongly mimics malicious phishing attempts designed to steal credentials.This insight reveals a key heuristic in Gmail’s algorithm: the absence of proper encryption combined with an immediate request for sensitive information is highly suspicious. It underscores the critical need for all login or data-entry pages to be served over HTTPS.
29 Aug 2019 - Email Geeks
Expert view
Expert from Email Geeks strongly recommended dual improvements. They advised adding actual descriptive text to any linked website, alongside implementing SSL, especially if the page is a login portal. This comprehensive approach helps legitimize the page's appearance and enhance its trustworthiness in the eyes of automated filters.The expert's suggestion highlights that both content and security protocols are equally important. A page that looks sparse and suspicious, even with SSL, might still raise flags, just as a text-rich page without SSL would.
29 Aug 2019 - Email Geeks
What the documentation says
Official documentation from email providers and security organizations provides clear guidelines on how to prevent emails from being marked as phishing. These documents consistently highlight the critical role of secure connections (HTTPS), comprehensive content on linked pages, and robust email authentication protocols like SPF, DKIM, and DMARC. They emphasize that any element that could be misinterpreted as a phishing attempt—whether technical or content-related—must be addressed. Adhering to these documented best practices is fundamental for maintaining a trustworthy sender identity and ensuring email deliverability.
Key findings
HTTPS is mandatory: Technical documentation universally stresses that all pages requesting sensitive user information, such as login credentials, must be served over HTTPS.
Content context matters: Official security guides recommend that linked login pages should contain more than just input fields; they should provide clear context and branding to prevent suspicion.
Authentication is key: Proper implementation of email authentication standards (SPF, DKIM, DMARC) is crucial for email providers to verify the sender's legitimacy and reduce phishing flags. For a simple overview, refer to our guide to DMARC, SPF, and DKIM.
Phishing patterns: Documentation warns that anything mimicking common phishing tactics, such as suspicious links or lack of security indicators, will trigger automated systems.
Domain safety: Ensuring the overall safety of your domain, as assessed by tools like Google Safe Browsing, is paramount, as an unsafe domain will drastically impact email deliverability. Read more on fixing inbox placement when a domain is unsafe.
Key considerations
Secure your login pages with HTTPS: This is the most critical technical step to prevent phishing warnings when linking to pages requiring credentials.
Provide robust content on linked pages: Ensure your login pages offer clear branding, relevant information, and context beyond just the input fields. This builds trust and reduces suspicion.
Implement strong email authentication: Correctly configure and maintain your SPF, DKIM, and DMARC records to prove your sender legitimacy.
Regularly review security documentation: Stay updated with security best practices from major email providers and web security organizations. Fastmail's help article on Phishing explicitly mentions checking URLs for login pages.
Technical article
Fastmail documentation highlighted user vigilance for linked login pages. They stated that when a link in an email takes you to a login page, it's crucial to stop and carefully verify the URL in the browser's address bar. This practice is recommended because links to login pages are frequently exploited in phishing attacks.The documentation implies that even legitimate services should be aware that their login links carry a higher inherent risk of being mistaken for phishing. Therefore, ensuring the absolute legitimacy and security of these pages is paramount to avoid triggering both user and automated security warnings.
22 Mar 2025 - Fastmail
Technical article
Consumer Advice documentation provided general spam and phishing prevention strategies. They advised consumers to utilize email filters and block unwanted senders as fundamental steps to reduce the influx of spam and safeguard against phishing attempts. This focuses on the recipient's ability to control their inbox.For senders, this means that providing clear, legitimate emails that don't resemble spam is key. If emails are perceived as spam, users are more likely to block them, which can indirectly contribute to a negative sender reputation and increase the likelihood of future phishing flags.
