Summary
The question of whether to configure SSL or TLS on email sending domains for marketing purposes is nuanced. While SSL (Secure Sockets Layer) is largely deprecated in favor of TLS (Transport Layer Security) for securing internet communications, the core principle of encryption remains vital. For SMTP (Simple Mail Transfer Protocol), the standard for email transmission, TLS, specifically STARTTLS, is the prevailing method for encrypting the connection between mail servers. This encryption helps protect the privacy and integrity of emails as they travel across the internet. While direct evidence suggests that not having TLS configured for SMTP may not immediately lead to emails being rejected or significantly impact deliverability by major mailbox providers, it is undeniably a crucial security best practice. Furthermore, if your sending domain (or a subdomain) is used for hosting tracked links, images, or other web content within your emails, then securing these with an SSL/TLS certificate (HTTPS) is critical. This impacts how recipients perceive your emails and can indirectly influence sender reputation.
Key findings
- TLS is the standard: SSL is outdated; TLS is the recommended and current protocol for securing email transmissions (SMTP).
- SMTP encryption: TLS, particularly STARTTLS, encrypts the connection between sending and receiving mail servers, safeguarding email content during transit.
- Direct deliverability: While not directly impacting deliverability for the SMTP handshake, unsecured connections can flag recipient warnings, such as Gmail's open lock icon.
- Tracking domains: If your sending domain also hosts tracked links or images within emails, an SSL/TLS certificate is essential to secure these elements (HTTPS), which positively affects recipient trust and click-through rates. More on this can be found in our guide on SSL's importance for tracked links.
- Privacy and integrity: TLS minimizes the risk of emails being sent in plain text, protecting sensitive data from interception.
- General best practice: Implementing TLS is a low-effort way to enhance overall internet security and demonstrate a commitment to secure communication.
Key considerations
- Prioritize: While not always the highest deliverability priority, given its ease of implementation, it should be done.
- Google's transparency: Google actively monitors and reports on domains that do not use TLS encryption for email, indicating their emphasis on secure email environments. You can review Google’s safer email report to see global TLS adoption.
- Subdomain usage: Ensure that any subdomains used for email sending or tracking also have appropriate TLS configurations. We discuss this in more detail when asking what DNS records are needed for email sending subdomains.
- Domain reputation: While not a primary factor, a lack of TLS might signal a less reputable sender, particularly if your domain has a history of poor reputation or hijacking.
What email marketers say
Email marketers generally agree that while TLS (Transport Layer Security) for SMTP connections is a foundational security measure, its direct impact on email deliverability metrics like inbox placement is often seen as secondary compared to factors like sender reputation, content quality, and authentication (SPF, DKIM, DMARC). However, there's a strong consensus that TLS is a beneficial practice for maintaining trust and securing data in transit. The discussion often expands to the importance of SSL/TLS for tracked links and images, where its absence can more directly affect user experience and perceived trustworthiness.
Key opinions
- Security first: Marketers emphasize that TLS is crucial for encrypting email traffic and protecting data privacy, aligning with general internet security best practices.
- Indirect reputation: While not a direct deliverability signal, using TLS suggests a sender who cares about their infrastructure and recipient security, which can indirectly contribute to a positive sender reputation over time.
- Visual cues: Some mailbox providers, like Gmail, display visual indicators (e.g., an open lock icon) if an email was not sent over a TLS-encrypted session, potentially impacting recipient trust.
- Link and image encryption: SSL/TLS is highly recommended for any domains or subdomains used to host images or track clicks within emails, as this directly affects the security and professional appearance of the email content itself. Our article on how HTTPS/SSL for email links and images improves deliverability explores this in depth.
- Plain text avoidance: A key benefit of TLS is minimizing the transmission of email content in plain text across the internet, enhancing privacy.
Key considerations
- Low priority, but necessary: Many marketers view configuring TLS for SMTP as a 'should do' rather than a 'must do immediately' for deliverability, but acknowledge its overall importance.
- Subdomain implications: If a sending subdomain is also used for web assets (like images or landing pages), an SSL certificate is crucial for HTTPS access to those assets. This is especially true for subdomains used for marketing emails.
- Effort vs. reward: The general sentiment is that the effort to implement TLS for SMTP and SSL for web assets is minimal, yielding significant security and perceived trustworthiness benefits.
- Avoiding negative flags: Not using TLS might place your domain on internal 'unencrypted' lists at some mailbox providers, even if it doesn't immediately block mail.
Marketer view
Marketer from Email Geeks inquired about the necessity of TLS configuration on sending domains, noting that it didn't immediately seem like a standard practice. This highlights a common initial uncertainty among marketing professionals regarding the technical requirements for email security. The question suggests a need for clearer guidance on email encryption standards beyond basic sender authentication. It reflects the broader challenge marketers face in understanding the underlying infrastructure that impacts email deliverability and perception. While direct rejections might not occur, the perceived professionalism is key.
Marketer view
Marketer from Email Geeks clarified that SSL typically applies to HTTPS connections, while TLS encryption is the correct protocol for securing SMTP email transmissions. This distinction is vital for marketers to understand the appropriate use of each security layer in their email infrastructure. Understanding this technical difference ensures that efforts to secure email are correctly targeted. Proper TLS implementation secures the data in transit, preventing eavesdropping and tampering between mail servers, which is a fundamental aspect of secure email marketing.
What the experts say
Experts in email deliverability and security uniformly advocate for the use of TLS (Transport Layer Security) in email sending. While the absence of TLS for SMTP connections might not always result in direct email rejection by recipient servers, it is considered a fundamental aspect of responsible and secure email practices. The emphasis is often on the holistic view of email security, where TLS contributes to data integrity, privacy, and ultimately, a more trustworthy sending ecosystem.
Key opinions
- Mandatory for modern email: Experts agree that at this point, there is no valid reason not to deliver emails using TLS. It's a standard expectation for secure communication.
- Data protection: The primary benefit of TLS is encrypting email messages between servers, ensuring the privacy and integrity of data in transit.
- Indirect deliverability factor: Although not a direct deliverability weighting factor for the SMTP handshake itself, avoiding plain-text transmission and adhering to security best practices contributes to a positive overall sender reputation. This can impact how your emails perform even if it is not a direct blocklisting reason.
- User trust signals: Mailbox providers like Gmail might display warnings (e.g., an open lock icon) for unencrypted emails, which can undermine recipient trust and engagement.
- Holistic security: SSL/TLS should extend beyond SMTP to secure all aspects of email, including tracked links and images hosted on the sending domain, to ensure end-to-end security and professional presentation.
Key considerations
- Avoid Google's 'unencrypted' lists: Not using TLS can result in a sender appearing in Google's transparency reports as not encrypting email, which is an undesirable signal for domain health.
- Certificate for web assets: If the same sending domain (especially subdomains) is used for HTTP/HTTPS web content (like tracking pixels or landing pages linked in emails), an SSL certificate is absolutely necessary. This impacts recipient trust more directly than SMTP TLS alone.
- Long-term reputation: While immediate deliverability changes might be small, consistently demonstrating secure practices through TLS helps build a robust and trusted sender reputation over the long term. This is a subtle but important factor for avoiding an email blocklist.
- Ease of implementation: Given that TLS configuration is generally a straightforward process with minimal lift for most senders, it is considered a fundamental step that should not be overlooked.
Expert view
Expert from LuxSci emphasizes that a popular and effective method for utilizing TLS is to secure SMTP. This process protects the transmission of email messages as they pass between various email servers. By encrypting this crucial leg of the email journey, senders can ensure that sensitive information remains confidential and is not exposed to unauthorized interception. This security measure is fundamental to maintaining email privacy, a key concern for both senders and recipients. Implementing TLS on SMTP connections is a standard practice in modern email infrastructure, contributing significantly to a secure communication environment and safeguarding against potential data breaches.
Expert view
Expert from Guardian Digital highlights that SSL/TLS protocols are instrumental in enhancing email encryption and securing sensitive data. These protocols offer a comprehensive guide to fortifying email communications against various threats. The continuous evolution of SSL/TLS ensures that email remains a secure channel for personal and business correspondence. Adopting these protocols is not just a best practice but a necessity for protecting data integrity and confidentiality in an increasingly vulnerable digital landscape.
What the documentation says
Official documentation and research consistently highlight TLS as the standard for securing email communications. While SSL has been superseded, the underlying concept of encrypting data in transit remains foundational. Documentation often focuses on the technical aspects of implementing STARTTLS for SMTP, as well as the broader security implications of using HTTPS for any web content (like tracking links or images) referenced within emails. These resources emphasize that secure transmission is a critical component of a trustworthy and compliant email ecosystem.
Key findings
- TLS is the modern standard: Security documentation unequivocally states that TLS has replaced SSL as the secure protocol for internet communication, including email.
- Opportunistic TLS: SMTP typically uses opportunistic TLS (STARTTLS), meaning it attempts to establish an encrypted connection, but will fall back to plain text if the receiving server doesn't support it. This secures as much traffic as possible.
- Data integrity and privacy: The core purpose of TLS for email is to prevent eavesdropping and tampering of messages during transmission between mail servers.
- Compliance and trust: Adhering to TLS best practices contributes to compliance with data protection regulations and builds trust with receiving mail servers and end-users.
- Broader security implications: Documentation often extends to recommending SSL/TLS for all related web assets (like tracking domains and images) to ensure consistent security from the email content to linked resources.
Key considerations
- Google's transparency reports: Google's public data on email encryption highlights the widespread adoption of TLS and identifies areas where encryption is lacking, reinforcing its importance.
- DMARC and MTA-STS: While opportunistic TLS is common, advanced security standards like MTA-STS (Mail Transfer Agent Strict Transport Security) are emerging to enforce TLS for specific domains, preventing downgrade attacks. These build on strong DMARC, SPF, and DKIM authentication.
- Certificate validation: For web assets, proper SSL/TLS certificate installation and validation are crucial to avoid browser warnings that could deter users from clicking links in emails.
- Impact on deliverability metrics: Though not always a direct blocking factor for SMTP, a lack of TLS for web assets (HTTPS) can negatively impact user engagement and perceived sender trustworthiness, indirectly affecting deliverability metrics.
Technical article
Documentation from Campaign Refinery emphasizes that for email marketers, TLS is the current standard for ensuring secure data transmission and robust deliverability. This highlights the industry's shift towards more modern and secure encryption protocols. The focus on TLS signifies an evolution from the older SSL protocols, advocating for enhanced security features that safeguard email content in transit. Adopting TLS is presented as essential for maintaining sender credibility and recipient trust in today's digital environment.
Technical article
Documentation from LuxSci confirms that securing SMTP with TLS is a widely adopted and effective method to protect the transmission of email messages between servers. This ensures that email content remains confidential during its journey across the internet. This practice is vital for preventing unauthorized access to email data, underscoring TLS as a fundamental component of secure email delivery. It also contributes to a positive sender reputation by demonstrating a commitment to privacy and security standards.
Related resources
6 resources
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