Does using HTTPS for email links directly affect deliverability?

While using HTTPS for email links and images might not directly improve your deliverability in isolation, it plays a significant role in maintaining a positive sender reputation and improving user experience. Mailbox providers value secure content, and consistent use of HTTPS indicates a trustworthy sender, potentially leading to better inbox placement over time. Learn more about if secure HTTPS links improve email deliverability .

What happens if I use HTTP links or images in my emails?

Using HTTP links or images in your emails can lead to several problems. Recipients may see security warnings in their webmail clients, images might fail to load, or links could behave inconsistently due to browser security policies like HSTS. These issues degrade the user experience and can cause recipients to perceive your brand as less secure or unprofessional, impacting engagement and potentially leading to unsubscribes or spam complaints.

Can mixed content (HTTP and HTTPS) cause problems in emails?

Yes, mixed content (a mix of HTTP and HTTPS elements) can definitely cause problems. When a secure (HTTPS) email client tries to load insecure (HTTP) resources, it often triggers warnings or blocks the content. This can result in broken images or links that don't function as expected, negatively impacting the visual presentation and functionality of your email. Our article on visible link domain mismatches or HTTP/HTTPS protocol discrepancies explains this further.

Is it enough if my website is HTTPS, but my email links are HTTP?

While having an HTTPS-enabled website is crucial, it's not enough if your email links or images still use HTTP. The security of the content within the email itself matters to the email client and the recipient. Even if the destination page is secure, an insecure link to it can still raise red flags. All assets and tracking domains directly referenced within the email should use HTTPS to provide a consistent and secure experience.

Why is it important to use HTTPS for links and images in email marketing? - Technical - Email deliverability - Knowledge base

In the digital landscape, security is paramount, and email marketing is no exception. We often focus on the content and call-to-actions within our emails, but the underlying protocols of our links and images are just as critical. Using HTTPS for all assets embedded or linked within your email campaigns isn't just a best practice, it's quickly becoming a necessity for maintaining strong sender reputation and ensuring your messages reach the inbox.

HTTPS, or Hypertext Transfer Protocol Secure, is the secure version of HTTP. It uses SSL/TLS encryption to protect the data exchanged between a user's browser and the website. This encryption prevents eavesdropping and tampering, safeguarding sensitive information and ensuring data integrity.

While email clients don't always behave exactly like web browsers, the principles of web security are increasingly influencing how emails are rendered and perceived. Ignoring HTTPS for your email assets can lead to a range of issues, from diminished trust to deliverability problems, and a poor user experience. Let's delve into why this seemingly small detail carries significant weight in your email marketing efforts.

The basics of HTTPS for email content

HTTPS (Hypertext Transfer Protocol Secure) encrypts the communication between a user's device and the server hosting the content. This is achieved through Transport Layer Security (TLS), which was formerly known as Secure Sockets Layer (SSL). When you use HTTPS, the data, whether it's a linked webpage or an image, is protected from being intercepted or altered by malicious third parties. This layer of security is a fundamental aspect of modern web browsing, providing confidentiality and integrity.

For email, the concern isn't just about preventing data breaches during transmission, but also about how email clients and webmail interfaces handle content. Many modern email environments are essentially web browsers, and they apply similar security rules. If an email contains links or images served over HTTP (insecure), these environments may flag them as mixed content. This can result in visual warnings or even outright blocking of the content, disrupting the user experience you intended.

The shift towards an HTTPS-everywhere internet is a clear signal. Major browser vendors and search engines, like

Google, actively promote and prefer HTTPS, even giving it a slight boost in search rankings. While email content doesn't directly influence SEO rankings, the underlying philosophy of valuing secure connections permeates the broader digital ecosystem, including how emails are handled by mailbox providers and their clients.

Understanding mixed content warnings

Mixed content occurs when an HTTPS page loads some resources, such as images, scripts, or stylesheets, over an insecure HTTP connection. In the context of email, if your email is rendered in a secure webmail client (which most are), and it tries to load an image or redirect through a link that uses HTTP, the browser might display a warning, block the content, or even mark the page as insecure. This degrades the user experience and can erode trust in your brand.

Impact on deliverability and sender reputation

While using HTTP links or images might not immediately land your emails in the spam folder, it subtly impacts your sender reputation and email deliverability. Mailbox providers and spam filters are constantly evaluating signals to determine the legitimacy and trustworthiness of incoming mail. An email with all secure links and images (HTTPS) projects an image of professionalism and attention to security, which contributes positively to your overall sending reputation.

Conversely, emails containing insecure HTTP elements can raise red flags. Even if they don't trigger an immediate block, they can be perceived as less trustworthy. This can lead to your emails being placed in the spam or junk folder more frequently, as discussed in our guide on how HTTP links affect email deliverability. It's a cumulative effect: consistent use of insecure content signals a lack of care or, worse, potential malicious intent, even if unintended.

The perceived security of your links also affects recipient behavior. When a recipient sees a warning about insecure content or notices that a link is not HTTPS, they are less likely to click on it. This directly impacts your engagement metrics, such as click-through rates. Low engagement is a strong negative signal to mailbox providers, indicating that your emails might not be valuable or wanted by recipients. This, in turn, can further degrade your sender reputation, creating a vicious cycle that ultimately affects your email deliverability.

For specific insights, consider the importance of SSL/TLS for tracking domains. Our article on SSL for tracked links and images in email marketing provides a deeper dive into this topic. It highlights how even click-tracking links, often managed by your Email Service Provider (ESP), should use HTTPS to maintain recipient trust and avoid warnings.

HTTP links and images

Security risk: Data exchanged is unencrypted and vulnerable to interception or modification.
Browser warnings: Can trigger mixed content warnings or block content in modern email clients.
Trust impact: Recipients may perceive your brand as less trustworthy or unprofessional.
Deliverability risk: Can negatively influence sender reputation and spam filtering.

HTTPS links and images

Enhanced security: All data is encrypted, protecting recipient privacy and data integrity.
Reliable display: Content loads without warnings, ensuring consistent user experience.
Increased trust: Builds confidence in your brand and encourages engagement.
Positive deliverability: Contributes to a stronger sender reputation and better inbox placement.

User experience and future considerations

Beyond the technical aspects, HTTPS plays a significant role in the user experience of your email campaigns. When a recipient opens an email, they expect all content to load seamlessly and without security warnings. If images fail to display or links trigger browser security alerts, it creates a frustrating and untrustworthy experience, potentially leading to immediate unsubscribes or even spam complaints. This is particularly true for users of webmail clients like

Gmail and

Outlook, which are essentially web applications and apply similar security rules.

One specific issue that can arise from using HTTP links that redirect to HTTPS is related to HTTP Strict Transport Security (HSTS). As noted by an expert in the field, if an HTTP link redirects to an HSTS-enabled HTTPS site, it might work on the first click. However, subsequent attempts to open that same link (or other HTTP links using the same redirect CNAME branding) could fail until the browser cache is cleared. This creates an inconsistent and unreliable experience for the user, undermining your marketing efforts.

The trend towards stricter security measures is only accelerating. Browsers like

Chrome, for example, have increasingly tightened their policies against mixed content. This means that an image served over HTTP within an email, even if the email client is HTTPS, might simply not load for the recipient. For more details on this, a relevant resource is Google doubles down on HTTPS and what it means for email marketers.

Issue	Impact on user	Impact on deliverability
Mixed content warnings	Browsers display security warnings, eroding trust.	Can negatively influence sender reputation over time.
Broken images	Images may not load, degrading visual appeal and message clarity.	Poor engagement signals lower email quality.
HSTS-related failures	Inconsistent link behavior due to browser caching.	Can lead to frustration and reduced click-through rates.
Perceived insecurity	Recipients are hesitant to click on insecure links.	Low engagement rates signal a negative sender reputation.

Implementing HTTPS for your email assets

Migrating to HTTPS for your email assets is a straightforward process, but it requires attention to detail. First, ensure that all landing pages, websites, and content delivery networks (CDNs) hosting your images are configured to use HTTPS. If your domain isn't fully HTTPS-enabled, you can obtain an SSL certificate from a trusted provider like

Cloudflare or

Let's Encrypt, and configure your web server accordingly.

Next, update all links and image sources within your email templates to use the HTTPS protocol. This includes standard hyperlinks, image src attributes, and any tracking links provided by your Email Service Provider. If your ESP offers a custom tracking domain, ensure it's configured with an SSL certificate. This is critical for preventing non-HTTPS engagement tracking from impacting your campaigns.

Finally, after making the changes, rigorously test your emails across various email clients, devices, and webmail providers. This will help you identify any remaining HTTP links or images and ensure that all content loads correctly and securely. Proactive testing is key to a smooth transition and maintaining optimal email performance.

Views from the trenches

Best practices

Always use HTTPS for all links and images within your email campaigns, even for simple tracking pixels.

Ensure your content delivery network (CDN) and any custom tracking domains have valid SSL certificates.

Regularly test your emails across different clients to confirm all content loads securely.

Common pitfalls

Ignoring browser warnings for mixed content, which can lead to images not displaying.

Assuming a website's HTTPS status automatically applies to all email content.

Overlooking HTTP redirects to HTTPS, which can cause HSTS issues for repeat clicks.

Expert tips

Google's push for HTTPS on the web indicates a similar preference within their email ecosystem.

Even minor security warnings can erode subscriber trust and impact engagement rates.

Embrace encryption across your entire email infrastructure, including your sending domains.

Expert view

Expert from Email Geeks says: While not a direct deliverability blocker, HTTPS for links will become increasingly critical in the future, as browsers are already issuing warnings for non-HTTPS content, which will eventually lead to display issues in emails.

October 1, 2021 - Email Geeks

Marketer view

Marketer from Email Geeks says: Using HTTP links that redirect to HTTPS can lead to issues with HSTS (HTTP Strict Transport Security), causing subsequent attempts to open the same link to fail until the browser cache is cleared.

October 1, 2021 - Email Geeks

Secure your email experience

The importance of using HTTPS for links and images in email marketing cannot be overstated. It's a foundational element of modern web security that extends directly into your email campaigns, influencing everything from recipient trust and user experience to your overall sender reputation and deliverability. By prioritizing secure connections, you demonstrate a commitment to your recipients' privacy and ensure your email content renders correctly, leading to higher engagement and better results.