Summary
The question of whether sporadic TLS encryption rates are common for bulk email senders utilizing opportunistic TLS is a significant concern within the email deliverability community. While some anecdotal evidence from ESPs suggests this is a widespread phenomenon, particularly around late 2018, data from other major senders doesn't always support this claim. This discrepancy highlights the complexity of TLS negotiation in a dynamic internet environment and its impact on email security and deliverability. Understanding the nuances of opportunistic TLS is crucial, as it aims for encryption when available but delivers unencrypted if not, leading to varying encryption percentages.
Key findings
- ESP assertions: Some ESPs claim that sporadic TLS encryption rates are a common issue observed across all bulk senders and ESPs, even citing verification from industry groups like M3AAWG.
- Divergent experiences: Despite these claims, not all bulk senders report experiencing sporadic TLS encryption rates, with some indicating consistent encryption over extended periods.
- Opportunistic TLS: The issue specifically applies to senders using opportunistic TLS, where encryption occurs only if the receiving server supports it. Senders with mandatory TLS will consistently see 100% encryption.
- Historical context: The trend of sporadic encryption rates reportedly began around November 2018 for some senders, suggesting a potential shift in recipient server behavior or network conditions.
Key considerations
- TLS configuration: Confirming whether your email sending infrastructure is configured for opportunistic or mandatory TLS is essential for interpreting encryption rate data. For more details, see our article on what causes a drop in TLS encryption percentage.
- Data collection and analysis: Reliable data points from multiple senders are needed to accurately assess the prevalence and extent of sporadic TLS encryption rates across the industry.
- Impact on deliverability: While not directly a deliverability blocker, lower TLS encryption rates can indicate underlying network or recipient server issues that might indirectly affect inbox placement or trust. Learn more about how Google penalizes for not using email encryption.
- Underlying causes: Investigating potential root causes such as network intermediaries, server configurations, or issues with specific receiving domains is important. As Twilio notes, many providers use opportunistic TLS by default, making this a common scenario.
What email marketers say
Email marketers often find themselves navigating the complexities of email encryption, particularly when dealing with bulk sending and opportunistic TLS. Their experiences vary widely, from seeing stable encryption rates to observing unexpected fluctuations. These discussions typically revolve around the practicality of implementing and maintaining TLS, its perceived impact on deliverability, and the challenges of confirming specific configurations with ESPs. The general sentiment is a desire for clarity and consistency in email security protocols to ensure reliable message delivery.
Key opinions
- ESP assurances: Some marketers are told by their ESPs that sporadic TLS encryption is a normal occurrence for all bulk senders.
- Lack of observed issues: Other marketers report not seeing any sporadic issues with their TLS encryption rates, even over extended periods, which contradicts the 'everyone' claim.
- Importance of TLS setting: There's a strong understanding among marketers that the TLS setting (opportunistic vs. mandatory) directly impacts observed encryption percentages.
- Platform-specific observations: Specific ESPs or platforms (e.g., Salesforce Marketing Cloud, Silverpop/WCA) are often mentioned in discussions about observed encryption rates.
Key considerations
- Verifying ESP claims: Marketers should seek independent verification or additional data points beyond what their ESP provides regarding widespread TLS issues.
- Monitoring encryption: Regularly monitoring TLS encryption rates through tools like Google Postmaster Tools can help identify unusual patterns. Understanding the ultimate guide to Google Postmaster Tools V2 can provide valuable insights.
- Communicating with ESPs: Engaging in detailed conversations with ESP support regarding specific TLS configurations and observed data can help clarify issues.
- Impact on sender reputation: While opportunistic TLS is widely accepted, consistent failure to encrypt when possible could subtly impact sender reputation or deliverability, as unencrypted emails are less secure. This could contribute to why emails go to spam.
Marketer view
An email marketer from Email Geeks states that their ESP indicates sporadic TLS encryption rates are common for all bulk senders and ESPs, a claim reportedly verified at M3AAWG, and this behavior has been observed since November '18 with opportunistic TLS settings.
Marketer view
An email marketer from Email Geeks reported that, upon reviewing their data for the past 120 days, they did not observe any issues with TLS encryption rates while using SFMC.
What the experts say
Experts in email deliverability and security offer a more nuanced perspective on sporadic TLS encryption rates. They emphasize that while some fluctuations are normal in an opportunistic environment, widespread and significant drops are often indicative of specific technical issues rather than a general industry trend. Their insights often focus on diagnostic approaches, the interplay of network components, and the importance of precise configuration and monitoring to maintain high encryption percentages and overall email health. They caution against broad generalizations and advocate for thorough investigation into specific cases.
Key opinions
- Not a universal trend: Experts generally disagree with the claim that sporadic TLS encryption rates are universally experienced by 'everyone' in bulk sending.
- Specific source identification: They believe that if a sender is experiencing sporadic rates, there's likely a specific, identifiable source or issue causing it.
- Technical investigation: Experts suggest direct communication and technical investigation (e.g., with the ESP's MTA team) to pinpoint the root cause of the problem.
- TLS negotiation complexities: The variability can stem from various factors, including network intermediaries, server load, and configuration differences between sending and receiving mail transfer agents (MTAs).
Key considerations
- Direct engagement: If facing sporadic TLS rates, engage directly with your ESP's technical team to investigate. Sometimes, specific issues like SSL/TLS key size errors can be a factor.
- Isolation of issues: It's crucial to determine if the issue is unique to your sending setup, specific recipient domains, or a broader trend impacting your ESP. This diagnostic approach is key to improving deliverability.
- Network path analysis: Consider the network path between your sending server and the recipient server. Intermediary mail gateways or firewalls might interfere with TLS negotiation. LuxSci explains how opportunistic TLS can be excellent but complicated to implement reliably.
- Proactive monitoring: Implement robust monitoring for TLS encryption rates to detect deviations promptly rather than relying solely on anecdotal evidence or general statements.
Expert view
An expert from Email Geeks offered to communicate directly with the ESP experiencing the issue, suggesting a willingness to investigate the problem further.
Expert view
An expert from Email Geeks contradicted the widespread claim, stating that the issue of sporadic TLS encryption rates is 'definitely not everyone' and that direct communication could help pinpoint the source.
What the documentation says
Official documentation and technical specifications shed light on the design and intended behavior of TLS in email transport. RFCs define how TLS negotiation should occur, emphasizing that opportunistic TLS prioritizes delivery over encryption when a secure connection cannot be established. This foundational understanding helps in interpreting observed encryption rates, as it inherently allows for variability based on the capabilities and configurations of both sending and receiving servers across the internet. The documentation underscores that 100% TLS encryption is only guaranteed with forced TLS or specific network conditions.
Key findings
- TLS protocol flexibility: The TLS protocol itself, as defined in RFCs like RFC 5246, is designed to be adaptable, supporting various versions and cipher suites, which can lead to negotiation failures if parameters don't align.
- Opportunistic by design: Opportunistic TLS explicitly means that an encrypted connection is attempted, but if it fails, the email is sent unencrypted. This behavior is fundamental to its operation and implies that a non-100% rate is possible and expected under certain conditions.
- Network impact: Official documentation often acknowledges that network conditions, intermediary servers, and the configuration of recipient MTAs can influence the success rate of TLS handshakes.
- Security vs. delivery: The primary goal of opportunistic TLS is to deliver the email, with encryption as a desirable enhancement. This prioritisation inherently allows for unencrypted delivery when secure transport is not feasible.
Key considerations
- Understanding TLS versions: Outdated TLS versions or cipher suites on either the sending or receiving side can lead to negotiation failures. Ensuring support for modern TLS 1.2 or 1.3 is critical.
- Server configuration: Proper server configuration, including valid certificates and correct cipher preferences, is essential for maximizing opportunistic TLS encryption rates.
- DANE/TLSA records: For enhanced security beyond opportunistic TLS, consider implementing DNS-based Authentication of Named Entities (DANE) with TLSA records to enforce mandatory TLS for specific domains, preventing downgrade attacks.
- Monitoring and logging: Comprehensive logging of SMTP transactions and TLS negotiation results is vital for diagnosing sporadic encryption issues and understanding why specific connections fall back to unencrypted transport.
Technical article
RFC 5246 (IETF) explains that the Transport Layer Security (TLS) protocol ensures communication security over the internet by allowing client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery.
Technical article
The Twilio Blog notes that many email providers, including SendGrid, use opportunistic TLS encryption by default, highlighting its widespread adoption and primary goal of securing data when possible, without preventing message delivery.
Related resources
5 resources
Related pages
What is TLS encrypted email traffic and what causes a drop in its percentage?
Does Google penalize for not using email encryption and how does it affect deliverability?
What causes SSL/TLS key size errors in email SMTP transactions?
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