Summary
Using HTTPS/SSL for email links and images is widely considered a best practice for security and user trust, but its direct impact on email deliverability and performance (specifically inbox placement) is often debated among marketers and experts. While the security benefits are clear, the direct correlation to improved deliverability is more nuanced. Many believe it positively influences sender reputation and recipient trust, which indirectly aids deliverability.
Key findings
- Security: HTTPS provides encryption for data in transit, protecting against eavesdropping and tampering. This builds trust with recipients and internet service providers (ISPs).
- User Experience: Browsers often display warnings for HTTP content on HTTPS pages, potentially breaking the user experience or displaying insecure content warnings.
- Indirect Deliverability Impact: While not a direct ranking factor for email algorithms, maintaining a secure infrastructure, including HTTPS for all assets, contributes to overall domain reputation, which is a significant factor in deliverability. For more on this, see our article on how website SSL/TLS affects email deliverability.
- SEO Relevance: Google uses HTTPS as a ranking signal for website search results. Although email is different from web search, the general push towards a secure internet influences how email providers perceive sender trustworthiness. You can read more about Google's approach to HTTPS as a ranking signal.
- Tracking Domains: For email marketing, using HTTPS for tracking domains is particularly important to avoid potential deliverability issues and maintain recipient trust. Explore the importance of SSL for tracked links in email marketing.
Key considerations
- Consistency: Ensure all links and images within your emails, including those in footers or tracking links, use HTTPS. Mixed content (HTTP assets on an HTTPS page) can trigger security warnings.
- Certificate Management: Proper configuration of SSL certificates, especially for CDN-hosted images or custom tracking domains, is crucial to prevent certificate errors that can harm user experience and trust.
- Cost vs. Benefit: While free SSL certificates are widely available (e.g., Let's Encrypt), some organizations might hesitate due to perceived costs or complexity of wildcard SSLs. However, the benefits of improved trust and potential deliverability outweigh these concerns.
- Performance: HTTPS can have a minimal performance overhead due to encryption, but modern web servers and CDNs are optimized to mitigate this, making the impact negligible for most email assets.
- Monitoring: Regularly check your email links and image URLs to ensure they resolve correctly over HTTPS and that certificates are valid.
What email marketers say
Email marketers often prioritize practical results and anecdotal evidence when assessing the impact of technical configurations like HTTPS/SSL. While some acknowledge the general best practice of using HTTPS, they are primarily concerned with its direct effect on email deliverability, open rates, and click-through rates. Many have observed a positive correlation, suggesting that secure links and images contribute to a more trustworthy sending profile, which in turn can lead to better inbox placement and recipient engagement. There's also a clear understanding that misconfigurations can lead to immediate problems.
Key opinions
- General Best Practice: Marketers generally agree that using HTTPS for web pages and links is a good practice for overall web security and user trust, even if the direct email deliverability benefit is not immediately obvious.
- Perceived Deliverability Benefit: Many marketers believe that HTTPS for links and images can indirectly aid email deliverability by making emails appear more legitimate and secure to email service providers (ESPs) and recipients. This aligns with broader trends in online security. For more on this, check out what is the deliverability impact of non-HTTPS engagement tracking.
- No Direct Filter Impact (Often): Some marketers don't believe that email filters directly penalize HTTP links or images, but acknowledge that HTTPS is a foundational security element that contributes to overall domain health.
- User Trust: Ensuring all content, including images and links, is served securely helps maintain recipient trust and reduces friction points, which can positively impact engagement metrics like clicks. Read about how SSL can improve email deliverability.
Key considerations
- CDN Configuration: If using a Content Delivery Network (CDN) for image hosting, ensuring the CDN’s SSL certificate is properly configured for your domain is critical. Misconfigurations can lead to broken images or security warnings.
- Expense of Wildcard SSL: The perceived expense of wildcard SSL certificates can be a deterrent for some clients, even if the long-term benefits outweigh the initial cost. However, free options like Let's Encrypt make this less of an issue.
- Impact on Tracking: It is important to confirm that any link tracking mechanisms also utilize HTTPS to maintain consistency and prevent mixed content warnings. For more details on this, refer to our guide on whether HTTP tracking links affect email deliverability.
Marketer view
Email marketer from Email Geeks suggests always striving to use HTTPS for pages because it is inherently better. While they don't believe email filters directly care about this, HTTPS is still considered a positive factor overall. Images, however, might not matter as much in this context.
Marketer view
Email marketer from Quora indicates that creating unique links with personalization fields and attributes within email campaigns is most effective for increasing click-through rates and overall conversions, which implies secure links are part of this effective strategy.
What the experts say
Email deliverability experts typically emphasize the broader ecosystem of security and reputation when discussing HTTPS/SSL. While they acknowledge that HTTPS itself isn't a direct inbox placement algorithm factor, it forms a crucial part of a secure sending infrastructure. They often highlight the strong connection between general website security, domain reputation, and email performance, especially with major mailbox providers like Google. Evidence, even if not fully conclusive, points towards HTTPS being a contributing factor to overall sender trustworthiness.
Key opinions
- Indirect Deliverability Factor: Experts largely agree that while HTTPS might not be a direct deliverability signal like SPF or DKIM, it contributes to overall domain and sender reputation, which in turn influences inbox placement. In general, secure HTTPS links improve email deliverability.
- Google's Stance: There's a strong belief that Google, given its emphasis on HTTPS for SEO, extends this preference to its email properties (Gmail). This means secure links and images could implicitly benefit Gmail deliverability.
- Holistic View: Deliverability is viewed holistically. HTTPS is one component of a secure and trustworthy sending environment. Other factors include technical solutions from top performing senders.
- Evidence-Based Approach: While conclusive, publishable data might be scarce, experts often collect internal data that suggests positive correlation between full SSL implementation and improved email performance.
Key considerations
- SEO and Deliverability Connection: The increasing tie between search engine optimization (SEO), overall domain reputation, and email deliverability means that practices benefiting one area (like HTTPS for SEO) can spill over and benefit the other.
- Perceived Security Risk: ISPs and security filters are constantly evolving to protect users. Non-HTTPS links and images could be flagged as potential security risks, even if benign, leading to reduced inbox placement.
- Domain Reputation: Maintaining a strong and trustworthy domain reputation is paramount. Fully securing your domain with SSL/TLS for all aspects, including email assets, contributes positively to this reputation.
- User Expectation: As the internet shifts towards HTTPS by default, users increasingly expect secure connections. Emails that violate this expectation might be viewed with suspicion, impacting engagement.
Expert view
Email expert from Email Geeks confirms that they have been collecting data indicating HTTPS is important to Google across the board, for both pictures and links, especially footer links. This suggests a broad influence on how Google's systems perceive security.
Expert view
Email expert from SpamResource.com states that general web best practices, including HTTPS adoption, increasingly influence email deliverability. They emphasize that email security is intertwined with overall internet security trends, encouraging senders to align with secure protocols.
What the documentation says
Official documentation from major email service providers, security organizations, and industry bodies consistently advocates for the use of HTTPS/SSL for all web assets due to its inherent security benefits. While they may not explicitly state that HTTPS directly improves email deliverability algorithms, they emphasize its role in securing communication, protecting user data, and building trust. This foundational security is understood to contribute to a positive sender reputation, which is a key factor in how emails are processed and delivered.
Key findings
- Encryption and Integrity: HTTPS ensures that data transmitted between a user's browser and a server (where email images/links resolve) is encrypted and not tampered with. This prevents man-in-the-middle attacks.
- User Trust and Security Indicators: Browsers display clear security indicators (e.g., padlock icon) for HTTPS sites. Lack of HTTPS or mixed content can trigger warnings, undermining user trust and potentially impacting engagement with your links.
- Industry Standard: HTTPS has become the standard for secure web communication. Adhering to this standard demonstrates a commitment to security, which is favorable to ISPs assessing sender reputation. Learn about how to set up SSL click tracking.
- Sender Reputation: While not explicitly a spam filter trigger, a secure and consistent online presence (including HTTPS for all web assets linked from email) contributes to a positive overall sender reputation. This can indirectly improve inbox placement. For more information, read a practical guide to understanding your email domain reputation.
Key considerations
- Comprehensive Implementation: All external resources, including images hosted on CDNs and tracking links, should be served over HTTPS to ensure a fully secure experience and avoid warnings.
- Certificate Validity: Ensure your SSL/TLS certificates are valid, up-to-date, and correctly configured for all domains and subdomains serving content for your emails.
- Performance Overhead: While minimal with modern infrastructure, consider the slight performance overhead of encryption. Optimized servers and CDNs make this largely negligible for typical email assets.
- User Agent Behavior: Email clients and web browsers may treat mixed content (HTTP and HTTPS) differently, potentially blocking or warning about insecure elements, which can degrade the user experience and prevent images from loading.
Technical article
Documentation from Twilio advises on how to set up SSL click tracking to ensure secured embedded links when sending emails. This is crucial for optimal link tracking performance and user security, as it prevents potential warnings from browsers or email clients when recipients click tracked links.
Technical article
Documentation from Google for Developers indicates that they started using HTTPS as a ranking signal, even if lightweight at first. This signifies Google's push for a more secure web, which indirectly influences how all web assets, including those linked from emails, are perceived.
Related resources
8 resources
Related pages
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Does website SSL/TLS affect email deliverability?
Why is it important to use HTTPS for links and images in email marketing?
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