Summary
The enforcement of HTTP Strict Transport Security (HSTS) without careful planning and inter-departmental communication, particularly with marketing teams, can lead to significant email deliverability issues. This security policy, designed to force browsers to connect via HTTPS only, can inadvertently break HTTP-based email tracking links and embedded content. When IT teams implement HSTS without informing marketing, email campaigns can suffer from non-functional links, resulting in a poor user experience, reduced engagement, and potential damage to sender reputation. The core problem often stems from a disconnect where security priorities override awareness of email marketing infrastructure, which may still rely on HTTP for various elements. This highlights the critical need for collaborative efforts to ensure a seamless transition to a fully secure online environment.
Key findings
- Communication gap: Many IT and security teams enable HSTS without informing marketing departments, leading to unexpected problems.
- Broken links: Email tracking and embedded content links, often configured as HTTP, cease to function correctly when HSTS forces HTTPS-only connections for the domain.
- User experience degradation: Recipients encounter broken links or security warnings, which can erode trust and negatively impact brand perception.
- ESP compatibility: Some email service providers (ESPs) may not default to HTTPS for all tracking or link branding, or may even charge a premium for it, complicating HSTS adoption.
- Mixed content issues: HSTS exacerbates mixed content warnings by strictly enforcing HTTPS, causing problems if any email assets remain HTTP.
Key considerations
- Cross-functional collaboration: Establish clear communication channels between IT, security, and marketing teams before any major web security changes like HSTS are implemented.
- Pre-implementation audit: Conduct a thorough review of all email links, images, and embedded content to ensure they are HTTPS compliant prior to enabling HSTS. For more on the technical side, consider reviewing what is HSTS.
- ESP configuration: Verify that your email service provider supports and defaults to HTTPS for all tracking links and custom domains, updating settings as necessary.
- Proactive updates: Update all email templates and link structures to use HTTPS to prevent broken links post-HSTS activation. This is also important for why HTTPS is important for email marketing.
- Lessons from DMARC: Recognize that HSTS implementation issues parallel challenges faced with DMARC implementation, emphasizing the need for thorough testing and coordination.
What email marketers say
Email marketers frequently face the brunt of uncoordinated HSTS deployments, often discovering broken links and client complaints only after the fact. Their perspectives highlight the urgent need for better internal communication and for email service providers to uniformly support HTTPS for all tracking and branding elements. Marketers often feel caught in the middle, having to deal with the operational fallout and explain issues to clients that could have been avoided with proactive planning.
Key opinions
- Unforeseen impact: Marketers frequently express surprise and frustration when security updates like HSTS are rolled out without their knowledge, causing immediate campaign disruption.
- Client blame: Agencies and marketing teams often find themselves blamed for broken links, even when the root cause is an uncommunicated IT security change.
- Incomplete HTTPS adoption: Many marketers note that HTTPS is still not universally enabled across all marketing assets or by all ESPs, leading to vulnerabilities when HSTS is activated.
- Cost barriers: Some marketers report that certain ESPs may still charge additional fees for HTTPS link tracking, which can deter adoption.
- Security warnings: Mismatched protocols between HSTS-enforced domains and HTTP email links can trigger browser security warnings, deterring user engagement.
Key considerations
- Advocate for full HTTPS: Marketing teams should push for complete HTTPS adoption across all web and email assets to prevent mixed content issues. This includes addressing non-HTTPS engagement tracking.
- Verify ESP capabilities: Ensure your ESP supports and automatically implements HTTPS for all links, especially tracking and branded domains.
- Internal communication protocols: Work with IT and security to establish protocols for notifying marketing of any changes to domain security that could impact email links.
- Proactive testing: Implement testing procedures for email links after any website or security updates, similar to how one might address Chrome blocking mixed content.
- Educate stakeholders: Educate IT and security teams on the direct impact of HSTS on email deliverability and marketing effectiveness. More information can be found on fixing mixed content warnings.
Marketer view
A marketer from Email Geeks observed a sudden increase in clients reporting broken links, consistently tracing it back to unannounced HSTS enablement by IT teams.
Marketer view
A digital marketing manager from Reddit emphasized the importance of full HTTPS integration across all marketing assets to prevent disruption when new security protocols are introduced.
What the experts say
Experts in email deliverability and security universally agree that HSTS is a beneficial security measure, but its implementation without comprehensive planning and communication is a recipe for disaster. They emphasize that the problem isn't HSTS itself, but rather the failure of organizations to account for all their web assets, including email links, when rolling out such a stringent policy. The consensus is that ESPs also bear responsibility for ensuring universal HTTPS support to ease these transitions.
Key opinions
- Implementation, not HSTS, is the problem: HSTS is a robust security feature, but unintended consequences arise from enabling it without thorough preparation and cross-functional coordination.
- DMARC parallels: The issues with HSTS implementation mirror past challenges with DMARC, where security initiatives inadvertently caused email deliverability breakdowns.
- ESPs lagging: Some ESPs are perceived as behind the curve in universally adopting HTTPS for all click-tracking and branded links, contributing to the problem.
- SSL mismatch errors: When HTTP links are served from an HSTS-enabled domain, users encounter critical SSL mismatch errors, creating a highly negative and alarming experience.
- Undisclosed changes: Security teams often implement HSTS without informing marketing, directly leading to broken links and client complaints.
Key considerations
- Holistic planning: Ensure all web properties, including email links and tracking domains, are HTTPS compliant before deploying HSTS. For more about HSTS, consider what HSTS is used for.
- Vendor responsibility: ESPs must step up to universally support HTTPS for all clients and email functionalities, eliminating the need for manual configurations or premium charges.
- Comprehensive testing: Thoroughly test email links and their redirection behavior after any HSTS or SSL certificate changes to prevent broken experiences.
- Inter-departmental synergy: Foster better collaboration between IT/security and marketing to proactively address potential deliverability impacts of security measures. Similar issues can arise during new IP and subdomain warmup.
- Proactive problem solving: Address potential issues like DMARC implementation with the same level of caution and communication.
Expert view
An expert from Email Geeks commented that HSTS itself is not problematic; the core issue lies in its implementation without adequate preparation and coordination.
Expert view
An expert from SpamResource advised that comprehensive audits of all web assets, including email tracking URLs, are essential before implementing aggressive security headers like HSTS.
What the documentation says
Official documentation on HSTS and web security protocols consistently emphasizes the importance of secure connections. These resources highlight how HSTS (HTTP Strict Transport Security) is designed to protect websites from various attacks by enforcing HTTPS. However, they implicitly underscore that such stringent policies require all elements, including those served in emails, to be equally secure. The documentation confirms that issues like mixed content warnings and a lack of HSTS can lead to vulnerabilities and poor user experiences, necessitating a comprehensive shift to secure protocols across all digital touchpoints.
Key findings
- Mandatory HTTPS enforcement: HSTS is a security mechanism that compels web browsers to interact with a site exclusively over HTTPS, preventing insecure connections.
- Protection against attacks: Proper HSTS implementation safeguards against downgrade attacks, SSL-stripping, and man-in-the-middle attacks.
- Mixed content warnings: These warnings occur when a secure HTTPS page attempts to load insecure HTTP content, leading to a degraded user experience and potential security risks.
- Risk of non-HSTS: Without HSTS, applications remain vulnerable to various exploits, including cookie-hijacking attacks, compromising user data.
Key considerations
- Full HTTPS migration: All website content, including external scripts, images, and embedded resources, must be served over HTTPS before HSTS implementation. Learn more about the lack of HSTS vulnerabilities.
- Subdomain consideration: When enabling HSTS, decide whether to include subdomains (using the includeSubDomains directive), ensuring all are HTTPS compliant to avoid issues like broken links impacting Gmail deliverability.
- Preload list implications: Submitting a domain to the HSTS preload list makes the policy permanent for major browsers, making rollback extremely difficult if issues arise.
- Continuous monitoring: Regularly monitor for mixed content warnings and ensure all link protocols align with HSTS policies.
Technical article
Documentation from IONOS explains that HSTS significantly enhances HTTPS security by mitigating man-in-the-middle attacks, ensuring all future connections are secure.
Technical article
Documentation from Acunetix defines HSTS as a crucial web security policy that compels web browsers to interact with a site exclusively over a secure HTTPS connection.
Related resources
4 resources
Related pages
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