Does using HTTPS/SSL for email links and images improve deliverability or performance?
Matthew Whittaker
Co-founder & CTO, Suped
Published 1 Aug 2025
Updated 19 Aug 2025
7 min read
Email is a crucial communication channel for businesses, marketers, and individuals alike. Ensuring that your messages reach the inbox, rather than the spam folder, is paramount. One aspect that often comes up in discussions about email deliverability and performance is the use of HTTPS (Hypertext Transfer Protocol Secure) or SSL (Secure Sockets Layer, now largely replaced by TLS) for links and images within emails. Many wonder if securing these elements truly makes a difference.
The internet has largely shifted to HTTPS, driven by security concerns and search engine preferences. This article explores whether this same principle applies to email content, specifically regarding the security of embedded links and images, and how it impacts both the successful delivery and the loading speed of your emails.
The foundation of trust: secure content serving
HTTPS, or HTTP with TLS encryption, ensures that data transferred between a user's browser and a website remains private and secure. When you include links and images in your emails, they often point to external web servers. If these resources are served over HTTP, they lack this encryption. Modern email clients and web browsers prioritize security, and they are increasingly wary of insecure content.
In mixed content scenarios, where a secure HTTPS page tries to load insecure HTTP resources, browsers often block the HTTP content or display security warnings. This can lead to broken images or non-functional links in your emails, eroding recipient trust and potentially affecting engagement metrics. For example, most modern browsers will block HTTP content from being displayed on an HTTPS page due to security risks. Email clients behave similarly, prioritizing the user's safety.
Using HTTPS consistently across all your web properties, including the servers hosting your email assets, demonstrates a commitment to security. This signal of trustworthiness can indirectly influence how mailbox providers perceive your sending domain and content. If you're wondering why it is important to use HTTPS, it comes down to security and trust.
Best practice: consistency is key
Always strive to serve all content, including images and landing pages linked from your emails, over HTTPS. This eliminates mixed content warnings and ensures a seamless, secure experience for your recipients, which can positively impact your email domain reputation. Remember, the goal is to make your emails appear as legitimate and trustworthy as possible to both recipients and mailbox providers.
How HTTPS affects email deliverability
While an SSL certificate on your mail server doesn't directly affect whether an email lands in the inbox (that's more about email authentication standards like SPF, DKIM, and DMARC), the security of links and images within the email *can* impact deliverability. Mailbox providers, like Google and Yahoo, are increasingly scrutinizing email content for signs of phishing and malicious activity. Insecure links or images can raise red flags.
When email clients detect insecure elements, they might: 1) Display warnings to the user, discouraging interaction, or 2) Flag the email as potentially suspicious, increasing the likelihood of it landing in the spam folder. This is especially true for emails containing secure, verified links are less likely to be flagged as spam. Conversely, non-HTTPS engagement tracking can hurt your sender reputation.
Using HTTPS for your links and images, especially for tracking pixels or hosted images, helps maintain a consistent level of security within your email content. This consistency signals to mailbox providers that your emails are legitimate and safe, contributing positively to your email deliverability. It’s a proactive measure that reduces potential friction points with spam filters and improves the chances of your emails reaching the inbox.
Performance considerations
The performance aspect of using HTTPS for email links and images is generally positive, albeit with nuances. While some argue there's a slight overhead due to the encryption process, modern web servers and browsers are highly optimized to handle HTTPS with minimal performance impact. In fact, the benefits often outweigh any theoretical delays.
The main performance advantage comes from avoiding security warnings and content blocking. If an email client or browser blocks an HTTP image because the email itself is rendered in a secure context, the image simply won't load. This is a far worse outcome than a negligible delay. When all assets load correctly and without warnings, the recipient's experience is smoother, and the email content appears as intended. This also applies to situations where HTTP/HTTPS protocol discrepancies occur.
Furthermore, many content delivery networks (CDNs) are optimized for HTTPS, often providing faster global access to your assets. Using a CDN to serve your email images over HTTPS can actually improve load times for recipients worldwide, mitigating any concerns about performance overhead. The goal is to ensure your images load quickly and reliably.
Link tracking is a common practice in email marketing to measure engagement, but it introduces another point where HTTPS becomes critical. When a recipient clicks a tracked link, they are typically redirected through a tracking domain before reaching the final destination. If this tracking domain uses HTTP instead of HTTPS, it creates an insecure hop that can trigger warnings or even be blocked.
Many email service providers (ESPs) offer SSL click tracking or branded links with SSL, allowing you to configure your custom tracking domain to use HTTPS. This ensures that every step of the click journey is secure, from the initial click in the email to the final landing page. Using SSL for tracked links and images is important for deliverability.
Similarly, domain masking, where your links appear to originate from your own domain even if they're hosted elsewhere, should also leverage HTTPS. This consistency reinforces your brand's legitimacy and avoids any perceived discrepancies that could negatively affect your sender reputation or cause your emails to be flagged as spam. The shift to HTTPS for all web content, including email-related assets, is an industry best practice for both security and deliverability. HTTPS is HTTP with TLS encryption.
HTTP links and images
Security warnings: Email clients or browsers may display warnings about insecure content.
Content blocking: Images might not load, and links may not function.
Deliverability risk: Increased chance of emails landing in spam or being blocklisted.
User trust: Can undermine confidence in your brand.
HTTPS links and images
Enhanced security: All data is encrypted during transfer, protecting user privacy.
Improved deliverability: Reduced risk of spam filtering; signals legitimacy to ISPs.
Better performance: Consistent loading without blocking, potentially faster with CDNs.
Increased trust: Builds recipient confidence and brand credibility.
Final thoughts on HTTPS in email
In the evolving landscape of email marketing and security, the consistent use of HTTPS for all links and images within your emails is not just a best practice, but increasingly a necessity. It’s a foundational element of a strong sender reputation and ensures your messages are displayed as intended.
While there may be minor performance overheads, the significant benefits in deliverability, user trust, and avoiding content blocking far outweigh them. Prioritize securing all your email-related assets to enhance both your email performance and the recipient experience.
Views from the trenches
Best practices
Always use HTTPS for all links and images, including tracking URLs, to ensure consistent security and prevent mixed content warnings.
Utilize CDN services for hosting email images to improve load times and reliability, ensuring the CDN supports and enforces HTTPS.
Verify that your email service provider offers SSL for click tracking and branded links, and configure it correctly.
Regularly check your email previews across various clients to ensure all content, especially images, loads without security issues.
Common pitfalls
Mixing HTTP and HTTPS content within the same email can lead to broken images, non-functional links, and security warnings for recipients.
Ignoring the security of tracking domains, which can cause email clients to flag your messages as suspicious or untrustworthy.
Underestimating the impact of perceived security on recipient trust, leading to lower engagement and higher spam complaint rates.
Failing to update legacy email templates or asset paths to use HTTPS, resulting in outdated and insecure content delivery.
Expert tips
Consider that major mailbox providers, like Gmail, are increasingly aligning email deliverability signals with broader web security standards, including HTTPS.
Monitor your engagement metrics closely after implementing HTTPS for email assets to observe positive shifts in clicks and opens.
While direct deliverability impact from HTTPS on images might not be universally stated, the indirect benefits to user experience and trust are undeniable.
Remember that the cost of an SSL certificate for modern hosting is often minimal or free, making it an accessible best practice for everyone.
Marketer view
Marketer from Email Geeks says always use HTTPS for pages, but for pictures, it might not matter as much. They believe filters don't primarily care about this, but HTTPS is generally a good practice for security.
2019-07-02 - Email Geeks
Expert view
Expert from Email Geeks says their data shows HTTPS is important to Google across the board, including for images and especially footer links. Multiple clients observed increases after securing all content with SSL.
Google and 
Yahoo, are increasingly scrutinizing email content for signs of phishing and malicious activity. Insecure links or images can raise red flags.
