Summary
TLS encrypts email during transit, securing it from interception. While its direct impact on deliverability is debated, a secure connection enhances sender reputation and builds recipient trust. Issues like broken TLS connections can erode trust and potentially impact deliverability, especially with services like Gmail pushing for encryption. Many sources note the benefits of TLS are indirect. Opportunistic TLS (STARTTLS) attempts to encrypt connections but may fall back to unencrypted if negotiation fails, and this is generally considered acceptable. DANE and MTA-STS provide further security by validating endpoints, helping prevent downgrade attacks. Correct SMTP configuration and monitoring are vital to ensure TLS is properly implemented.
Key findings
- Encryption in Transit: TLS primarily encrypts email during transmission, protecting content from eavesdropping.
- Indirect Deliverability Impact: The effect on deliverability is often indirect, influencing sender reputation and recipient perception.
- Sender Confidence: A broken TLS connection can significantly decrease recipient confidence and trust in the sender.
- Opportunistic TLS (STARTTLS): Attempts to upgrade to TLS, but allows unencrypted fallback, prioritizing delivery over strict encryption.
- DANE and MTA-STS: Provide extra security by validating endpoints, mitigating downgrade attacks where possible.
- SMTP Responsibility: Technical issues related to TLS are primarily the responsibility of the SMTP server owners/administrators.
Key considerations
- Check Logs: Check SMTP error logs to troubleshoot TLS connection issues.
- Prioritize TLS: Configure systems to support TLS, even if opportunistic, and monitor for connection failures.
- Address 'Broken Lock' Issues: If recipients report 'broken lock' warnings in email clients, investigate and resolve the underlying TLS issues promptly.
- Implement DANE/MTA-STS: Evaluate and implement DANE/MTA-STS where applicable to further improve email security.
- Monitor TLS: Continuously monitor TLS connections for successful negotiation and any potential security vulnerabilities.
What email marketers say
9 marketer opinions
TLS (Transport Layer Security) encrypts email communications, enhancing security and potentially improving sender reputation and deliverability. While some sources suggest TLS indirectly boosts deliverability through increased sender confidence and security, others note that its absence might raise flags with email providers. Issues with TLS, like broken connections, can make recipients wary, negatively impacting sender confidence and deliverability. Implementation of DANE and MTA-STS can further secure email by validating endpoints. However, some servers may not support TLS, leading to unencrypted connections.
Key opinions
- Encryption: TLS encrypts email communications, protecting them from eavesdropping and tampering.
- Sender Reputation: Using TLS enhances email security and sender reputation, potentially improving deliverability.
- Decreased Confidence: Broken TLS connections can decrease recipient confidence and negatively affect deliverability.
- Indirect Impact: While TLS itself may not directly influence spam filtering, its absence can raise flags.
- Alternative Security: DANE and MTA-STS provide additional security layers by validating endpoints.
- Unencrypted Fallback: Some servers may not support TLS, resulting in a fallback to unencrypted connections.
Key considerations
- Check Error Logs: If you are having trouble establishing the session using TLS, check the error logs for clues
- Opportunistic TLS: Ensure your email server supports STARTTLS to encrypt connections when available.
- Implement DANE/MTA-STS: Consider implementing DANE and MTA-STS for enhanced email security and validation.
- Monitor TLS Connections: Regularly monitor TLS connections to identify and address any issues that may arise.
- Check Configuration: Configure TLS correctly to ensure secure email transmission. Ensure TLS is enabled for connections to Google helps protect sensitive data, potentially improving sender reputation and confidence.
Marketer view
Email marketer from Email Marketing Forum posits that while TLS itself might not be a direct factor in spam filtering, the lack of it could raise flags with some email providers. They state that using TLS contributes to a more secure setup, which could indirectly help with deliverability.
11 Nov 2024 - Email Marketing Forum
Marketer view
Email marketer from Reddit suggests that a broken TLS connection can make recipients wary of your emails and decrease confidence in the sender. It can also affect email deliverability because of Google's push to encrypt everything.
10 Feb 2023 - Reddit
What the experts say
3 expert opinions
TLS is an encryption method for securing email communication, particularly during transit. While it protects content from exposure, some experts believe its direct impact on deliverability is minimal, as major providers like Google still accept non-TLS encrypted emails. STARTTLS offers opportunistic encryption, upgrading connections to TLS when possible, but falling back to unencrypted if necessary. Experts do not necessarily believe that the lack of opportunistic TLS negatively effects delivery.
Key opinions
- Encryption Purpose: TLS encrypts email communications in transit, safeguarding content from unwanted access.
- Limited Deliverability Impact: Some experts suggest that TLS doesn't significantly affect deliverability, as major email providers still accept non-encrypted emails.
- Opportunistic Encryption: STARTTLS attempts to upgrade connections to TLS encryption, but reverts to unencrypted communication if TLS negotiation fails.
Key considerations
- SMTP Responsibility: Technical issues with SMTP sessions related to TLS are the responsibility of the SMTP server owners.
- Encryption Importance: While TLS may not directly impact deliverability, it remains an important tool for protecting sensitive email content.
- Delivery Success: Lack of opportunistic TLS may not have a negative impact on delivery.
Expert view
Expert from Spam Resource explains that STARTTLS offers opportunistic encryption, which means it attempts to upgrade an unencrypted connection to a TLS-encrypted connection. They also state that if encryption is not negotiated, the session will continue unencrypted. They do not believe the lack of opportunistic TLS negatively effects delivery.
3 Oct 2022 - Spam Resource
Expert view
Expert from Email Geeks shares that TLS doesn't matter that much in terms of deliverability, as Google accepts mail that is not coming over a TLS encrypted channel. However, she states that the issue is a technical problem with the SMTP session, and the folks who own the SMTP server are responsible for it.
22 Feb 2024 - Email Geeks
What the documentation says
3 technical articles
TLS encryption secures email communications, although its direct impact on deliverability isn't explicitly stated by all sources. Enabling TLS for Google connections protects data, potentially improving sender reputation. Opportunistic TLS encrypts if the receiving server supports it, but defaults to unencrypted delivery for broader reach, acknowledging downgrade risks. Proper SMTP configuration with appropriate TLS settings and versions is crucial for enhanced security.
Key findings
- Security: TLS encryption secures email communications, protecting sensitive data.
- Potential Reputation Improvement: Enabling TLS with Google connections might improve sender reputation and confidence.
- Opportunistic Encryption: Opportunistic TLS prioritizes delivery by encrypting when possible, but still delivering unencrypted if TLS isn't available.
- Downgrade Risk: Opportunistic TLS carries a risk of downgrade attacks.
- Configuration Importance: Proper SMTP configuration with the right TLS settings is crucial for secure email transmission.
Key considerations
- Enable TLS: Ensure TLS is enabled, especially for connections to major email providers like Google.
- Assess Downgrade Risk: Consider the risks associated with downgrade attacks when using Opportunistic TLS.
- Configure SMTP: Properly configure SMTP settings with appropriate TLS versions and security measures.
Technical article
Documentation from RFC Editor defines Opportunistic TLS as encrypting email communications if the receiving server supports TLS, but still delivering the email unencrypted if TLS is unavailable. It acknowledges the risk of downgrade attacks but prioritizes widespread email delivery.
8 Apr 2023 - RFC Editor
Technical article
Documentation from Google answers that TLS encryption helps secure email communication. While Google doesn't explicitly state it directly impacts deliverability, ensuring TLS is enabled for connections to Google helps protect sensitive data, potentially improving sender reputation and confidence.
6 Apr 2023 - Google
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