Summary
The consensus among experts, email marketers, and technical documentation is that while HTTP links may not always trigger spam filters directly, their use in email marketing is generally discouraged. The primary reasons include: a potential negative impact on user trust and engagement, the risk of triggering mixed content warnings, the possibility of degraded sender reputation, increased likelihood of being flagged by ISPs and email clients, and the overall industry push towards secure HTTPS connections. Upgrading to HTTPS is consistently recommended to improve deliverability, enhance security, and align with best practices.
Key findings
- No Direct Spam Trigger (Usually): HTTP links do not always directly trigger spam filters.
- Erosion of User Trust: HTTP links can erode user trust and negatively impact engagement.
- Mixed Content Warnings: HTTP links contribute to mixed content warnings, signaling a lack of security.
- Degraded Sender Reputation: Over time, using HTTP links can lead to a degraded sender reputation.
- ISP/Client Flags: HTTP links increase the likelihood of being flagged by ISPs and email clients.
- HTTPS is Preferred: The industry is moving towards HTTPS as a standard for secure communication.
- Delivery Shift Observed: A shift in delivery rates favoring HTTPS over HTTP has been observed.
- Webmail Preference: Webmail providers are more likely to give preference to secure (HTTPS) sites.
Key considerations
- Prioritize HTTPS: Prioritize HTTPS links in all email marketing efforts.
- Ensure Security: Ensure all links are secure to safeguard user data and maintain trust.
- Minimize Vulnerabilities: Minimize vulnerabilities by adhering to modern security protocols, such as HTTPS.
- Update Existing Links: Update existing HTTP links to HTTPS to improve deliverability and security.
- Webmail Optimization: Optimize emails for webmail providers by ensuring all links are secure.
- Long-Term Deliverability: Consider the long-term impact of HTTP links on deliverability and sender reputation.
- Trust Signals: Treat HTTPS as a trust signal to build stronger relationships with recipients.
- Avoid mixed content: Avoid creating mixed content (HTTP on HTTPS pages) to protect user privacy and security.
What email marketers say
9 marketer opinions
While HTTP links may not trigger spam filters directly, they can negatively impact email deliverability by eroding user trust, potentially raising red flags with ISPs and email clients, and degrading sender reputation over time. Most sources recommend using HTTPS links to ensure better deliverability and credibility.
Key opinions
- No Direct Penalty: Using HTTP links does not always directly trigger spam filters.
- Trust & Security: HTTPS links improve trust and security, positively influencing deliverability.
- User Perception: HTTPS links prevent browsers from flagging emails as unsafe, impacting user perception and engagement.
- Sender Reputation: HTTP links can degrade sender reputation over time.
- Red Flags: HTTP links can raise red flags with ISPs and email clients.
- Redirects: HTTP links, especially when redirecting, can trigger spam filters due to security concerns.
Key considerations
- Prioritize HTTPS: Always use HTTPS links to maintain deliverability and credibility.
- Security Concerns: Address security concerns by ensuring all links are secure.
- User Experience: Improve user experience by preventing browser warnings through the use of HTTPS.
- Sender Reputation Management: Proactively manage sender reputation by using HTTPS links.
- ISP/Client Standards: Align with ISP and email client standards by using secure links.
Marketer view
Email marketer from Sendinblue explains that HTTPS links contribute to a safer user experience and can prevent browsers from flagging emails as potentially unsafe. They suggest that while it's not a direct spam trigger, it can impact user perception and engagement.
22 Jul 2024 - Sendinblue
Marketer view
Email marketer from Email Geeks says using HTTP links stands out and should be highly discouraged.
4 Nov 2021 - Email Geeks
What the experts say
6 expert opinions
Experts generally advise against using HTTP links in email marketing due to potential deliverability issues and eroded trust. While not always a direct spam trigger, HTTP links can lead to mixed content warnings, reduced engagement, and may be penalized by webmail providers and search engines. Upgrading to HTTPS is recommended for security, better rankings, and improved deliverability.
Key opinions
- Avoid HTTP Links: Avoiding HTTP links is considered a best practice in email marketing.
- Delivery Shift: There has been a noticeable shift in delivery rates favoring HTTPS over HTTP.
- Google Penalties: Google penalizes non-HTTPS pages, and Gmail might follow suit.
- Mixed Content Issues: HTTP links can lead to mixed content warnings, eroding user trust.
- Webmail Preference: Webmail providers favor secure sites (HTTPS).
- Connectivity Issues: Using HTTP redirectors can cause connectivity errors.
Key considerations
- Upgrade to HTTPS: Transition to HTTPS as soon as possible to avoid potential deliverability problems.
- Security: Ensure all links are secure to improve user trust and prevent errors.
- User Experience: Provide a secure and seamless user experience by avoiding mixed content warnings.
- Webmail Optimization: Optimize for webmail providers by using secure links.
- Ranking Signals: Recognize HTTPS as a ranking signal and prioritize it in email marketing efforts.
Expert view
Expert from Spam Resource explains that the transition from HTTP to HTTPS is important for preventing mixed content warnings in email, which can erode trust in email marketing. Emails containing mixed content may get lower engagement.
23 Feb 2025 - Spam Resource
Expert view
Expert from Email Geeks shares a personal experience where using an HTTP Sendgrid redirector URL led to a “can’t connect securely” error in Mail.app.
23 Jul 2024 - Email Geeks
What the documentation says
5 technical articles
Technical documentation indicates that while HTTP links may not be directly penalized by spam filters, their use is discouraged due to security vulnerabilities, potential for mixed content warnings, and the overall push toward secure (HTTPS) connections. Using solely HTTPS is recommended for improved user trust, security, and a better user experience.
Key findings
- Mixed Content Warnings: Gmail may display warnings for messages containing mixed content (HTTP and HTTPS).
- No Direct Penalties: Explicit penalties for HTTP links are not directly mentioned, but negative impacts exist.
- User Trust: HTTP can negatively impact user trust and perception.
- Browser Blocking: Browsers actively block mixed content, especially HTTP content on HTTPS pages.
- Security Imperative: HTTPS ensures encrypted and secure communication.
Key considerations
- Migrate to HTTPS: Transition entirely to HTTPS to avoid becoming outdated and affecting user trust.
- Prioritize Security: Prioritize secure communication by avoiding HTTP.
- Modern Protocols: Use current security protocols like HTTPS to reduce vulnerabilities.
- Open Rates: Delivering solely HTTPS content suggests a potential improvement in open rates.
- Vulnerability Reduction: Using HTTPS helps reduce the risk of security vulnerabilities in communications.
Technical article
Documentation from Mozilla explains that browsers actively block mixed content (HTTP content on HTTPS pages) and suggests that delivering content solely over HTTPS is best practice for security and user experience. They also suggest this may result in a better open rate.
20 Aug 2021 - Mozilla Developer Network
Technical article
Documentation from RFC Editor recommends migrating entirely to HTTPS. While not explicitly penalizing HTTP links, the push toward secure connections means that HTTP can become outdated and affect user trust.
20 Jun 2023 - RFC Editor
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