Summary
Using HTTPS/SSL for email links and images is not typically a direct factor for email deliverability filters, but it is a critical security best practice that profoundly impacts recipient trust, content rendering, and overall sender reputation. Email clients and web browsers increasingly flag or block insecure HTTP content, leading to display issues, security warnings, and a diminished user experience. By ensuring all content is served over HTTPS, senders reinforce their credibility, prevent negative user signals, and contribute to a more secure and reliable email environment, which collectively enhances long-term deliverability and performance. This aligns with a broader web trend toward ubiquitous HTTPS, indicating its future importance for email success.
Key findings
- Indirect Deliverability Impact: While not a direct spam filter criterion, HTTPS significantly influences deliverability indirectly by building recipient trust, preventing security warnings, and ensuring content loads correctly, all of which reduce negative signals.
- Recipient Trust and Experience: Using HTTPS prevents 'mixed content' warnings or content blocking, which can deter user engagement, negatively affect sender reputation, and lead recipients to mark emails as suspicious.
- Google's Emphasis: Google considers HTTPS important for images and links, especially footer links, tying it to SEO and domain reputation, which can indirectly influence Gmail deliverability.
- Future Standard: The web is increasingly moving towards an all-HTTPS standard, implying that non-secure content may be more frequently penalized or flagged by email clients and Internet Service Providers (ISPs) in the future.
Key considerations
- Security Best Practice: Always use HTTPS for all linked and embedded content within emails to maintain a secure email environment, prevent browser or email client warnings, and contribute to overall data integrity.
- Avoid Mixed Content Warnings: Insecure HTTP content loaded within an email can trigger 'mixed content' warnings, prevent images from loading, or cause security alerts for recipients, negatively impacting user experience and trust.
- Enhance Sender Reputation: Consistent use of HTTPS contributes positively to your sender reputation over time by demonstrating trustworthiness and professionalism, which indirectly aids long-term deliverability.
- Content Loading Reliability: Using HTTPS ensures that images and other linked content load reliably across various email clients without display issues or security-related blocks.
What email marketers say
10 marketer opinions
The use of HTTPS for email links and images is a universally recognized best practice, though its impact on deliverability is primarily indirect. While not a direct filter for spam, secure connections are fundamental for fostering recipient trust and ensuring a seamless user experience. Modern email clients and browsers increasingly prioritize security, often flagging, blocking, or warning about insecure HTTP content. Such warnings can disrupt content loading, reduce engagement, and negatively affect a sender's credibility, ultimately harming long-term deliverability and performance by eroding sender reputation. Adopting HTTPS for all email assets aligns with broader web security trends and signals a professional, trustworthy sender.
Key opinions
- Indirect Deliverability Boost: HTTPS does not directly bypass spam filters but significantly enhances deliverability by positively influencing recipient behavior and sender reputation.
- Crucial for Trust & Security: Secure links and images prevent security warnings, build recipient confidence, and protect against content manipulation.
- Enhanced Content Loading: Ensures images and linked content load reliably across various email clients, avoiding 'mixed content' issues and display problems.
- Reputation Impact: A secure email environment consistently boosts sender reputation by demonstrating professionalism and trustworthiness, a key factor for long-term deliverability.
- Google's Preference: Google specifically values HTTPS for links and images, connecting it to SEO and domain reputation, which can influence Gmail deliverability.
Key considerations
- Universal HTTPS Adoption: Always serve all images, links, and other embedded content within emails via HTTPS to maintain a secure and professional presence.
- Prevent Negative Signals: Avoid insecure HTTP content to prevent email clients from displaying warnings or blocking content, which can reduce engagement and signal untrustworthiness.
- Improve User Experience: Securely loaded content ensures a smooth, uninterrupted recipient experience, encouraging clicks and interactions.
- Long-term Reputation Building: Consistent use of HTTPS contributes to a robust sender reputation, which is vital for sustained deliverability performance over time.
Marketer view
Marketer from Email Geeks explains that you should always try to use HTTPS for pages, noting that while filters might not care, HTTPS is generally good practice.
25 Dec 2023 - Email Geeks
Marketer view
Marketer from Email Geeks shares data indicating that HTTPS is important to Google for both images and links, especially footer links, suggesting increases after clients implemented SSL. He adds that he is trying to confirm if SSL helps with Gmail deliverability, noting that SEO and search are tied to domain reputation and email performance, and SEO is affected by SSL.
13 Feb 2022 - Email Geeks
What the experts say
2 expert opinions
While the direct impact of HTTPS/SSL on email deliverability filters may not be immediate, its adoption for email links and images is a crucial best practice for long-term success. The web is rapidly shifting towards an all-HTTPS standard, meaning browsers and email clients are increasingly flagging or warning users about unencrypted HTTP content. Such warnings can significantly reduce user engagement, diminish trust, and negatively affect click-through rates. Therefore, consistently hosting all email assets on an HTTPS server is essential to prevent future deliverability challenges, ensure content integrity, and maintain a professional, trustworthy sender image, with any performance overhead typically being negligible.
Key opinions
- Future Deliverability Factor: While not currently a direct factor for spam filters, HTTPS is increasingly becoming a prerequisite for optimal deliverability as web standards evolve towards universal encryption.
- Enhances User Trust: The absence of HTTPS triggers browser security warnings, which can deter recipients from engaging with links and reduce their trust in the sender.
- Ensures Content Integrity: Using HTTPS helps guarantee that all images and linked content load correctly within emails without being blocked or flagged by email clients, preserving the intended message.
- Aligns with Web Evolution: Embracing HTTPS for email content proactively aligns your email program with the broader internet trend towards ubiquitous security, preventing future compatibility or warning issues.
- Negligible Performance Impact: Any minor performance overhead introduced by the SSL handshake is generally offset by modern web optimizations and is outweighed by the security and trust benefits.
Key considerations
- Prioritize HTTPS Implementation: Make it a standard practice to host all images and linked content within your emails on HTTPS servers to ensure future compliance and avoid potential issues.
- Prevent Negative User Signals: Use HTTPS for all email assets to avoid 'not secure' warnings that can lead to reduced engagement, lower click-through rates, and a diminished sender reputation.
- Secure Content Display: Ensure all visuals and links load reliably across different email clients by serving them over HTTPS, which prevents broken content or security alerts.
- Strategic Future-Proofing: Adopting HTTPS for email is a proactive measure that future-proofs your campaigns against evolving security protocols and browser/email client preferences, ensuring long-term email effectiveness.
Expert view
Expert from Spam Resource shares that while using HTTPS for email links and images may not directly improve deliverability, it is a recommended practice as the web is moving towards an all-HTTPS standard. Browsers are increasingly warning users about unencrypted links, which can lead to reduced user engagement and clicks. Therefore, hosting all images and links on an HTTPS server is a good practice for user trust and avoiding future issues, even if the direct deliverability impact is not explicit.
9 Mar 2023 - Spam Resource
Expert view
Expert from Word to the Wise explains that while moving from HTTP to HTTPS for email links may not immediately impact deliverability, it will likely do so in the future. Browsers and email clients are increasingly preferring HTTPS URLs, with some already marking HTTP pages as 'not secure.' This trend suggests that ISPs may eventually flag non-secure content, or email clients might display warnings, which would negatively affect email reach and user trust. Therefore, using HTTPS helps ensure emails are delivered without warnings and with all content intact. For performance, HTTPS introduces a slight overhead from the SSL handshake, but this is usually minor and often balanced by modern web optimizations.
19 Oct 2024 - Word to the Wise
What the documentation says
5 technical articles
Consistently utilizing HTTPS for all email links and images is universally advocated as a critical security practice, even though its effect on deliverability is primarily indirect. Major providers like Google, Twilio SendGrid, Cloudflare, MDN Web Docs, and OVHcloud all emphasize that serving content over secure connections prevents frustrating browser security warnings, ensures reliable content display, and significantly boosts recipient trust. While not a direct filter criterion, these factors collectively enhance user engagement and positively reinforce sender reputation, ultimately contributing to better email performance and long-term deliverability. Embracing HTTPS for email content aligns with the broader web's move towards ubiquitous security, safeguarding the user experience and your brand's credibility.
Key findings
- Universal Industry Support: Leading email service providers and web security experts universally recommend using HTTPS for all email content due to its security and user experience benefits.
- Prevention of Security Warnings: HTTPS prevents 'mixed content' or browser security warnings that can disrupt content loading, alarm recipients, and negatively impact engagement.
- Enhances Recipient Trust: Secure links and images are crucial for building and maintaining recipient trust, which directly influences how they perceive and interact with your emails.
- Indirect Deliverability Aid: By improving user experience, preventing warnings, and fostering trust, HTTPS indirectly strengthens sender reputation and overall email deliverability.
- Reliable Content Display: Ensures that images and linked resources load correctly and consistently across various email clients, avoiding display issues caused by insecure content.
Key considerations
- Prioritize Secure Links: Always embed links and images in your emails using HTTPS to ensure a secure environment and prevent content issues.
- Avoid Mixed Content: Strictly avoid including HTTP-served content within an HTTPS-based email, as this can trigger warnings or content blocking by email clients.
- Boost User Engagement: Secure content fosters a positive user experience, encouraging higher engagement rates and reinforcing brand professionalism.
- Strengthen Sender Reputation: Consistent use of HTTPS signals trustworthiness to both recipients and ISPs, contributing positively to your long-term sender reputation and deliverability.
Technical article
Documentation from Google Support (Gmail) implies that using HTTPS for email links and images contributes to a secure email environment, which is indirectly beneficial for deliverability. Google's sender guidelines emphasize the importance of secure connections (TLS) for email transmission and avoiding security warnings, which could arise from loading insecure content (HTTP links or images) within an email, potentially affecting user trust and indirectly, deliverability.
21 Jun 2021 - Google Support (Gmail)
Technical article
Documentation from Twilio SendGrid emphasizes the importance of secure connections for email, including offering HTTPS for link branding and tracking domains. While the main focus is on TLS for email transmission, they support and recommend using HTTPS for all web content linked or embedded within emails (like images) to ensure security, prevent browser warnings, and improve user trust, which indirectly aids deliverability.
15 May 2022 - Twilio SendGrid Docs
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