Does using TLS matter for email deliverability or inbox placement?

Summary

The use of TLS (Transport Layer Security) for email transmission is generally considered important, primarily for security purposes, but its direct impact on email deliverability and inbox placement is a complex and debated topic. Most sources agree that TLS encrypts email content during transit, protecting it from eavesdropping and tampering. However, opinions diverge on whether this encryption directly translates to improved deliverability. Some experts suggest that not using TLS can negatively impact sender reputation, as a significant portion of email traffic is now TLS encrypted, and mailbox providers may view it as a negative signal. Others emphasize that as long as authentication methods like SPF, DKIM, and DMARC are properly configured, the absence of TLS may not significantly affect deliverability. Compliance with platform-specific requirements, like Exchange Online's mandate for TLS 1.2, is essential for mail flow within those ecosystems. Additionally, some sources advise disabling older TLS versions for security reasons, while others recommend falling back to plain text if a secure connection cannot be established. Emerging technologies like SMTP TLS Reporting can aid in detecting man-in-the-middle attacks, indirectly contributing to deliverability.

Key findings

  • Encryption Focus: TLS encrypts email content during transit, safeguarding it from unauthorized access.
  • Sender Reputation: Some email providers consider TLS a factor in sender reputation, potentially influencing deliverability.
  • Security Best Practice: Implementing TLS signals a commitment to secure practices, which can be viewed favorably by mailbox providers.
  • Limited Direct Impact: Some sources indicate that TLS does not directly influence deliverability metrics.
  • Platform Requirements: Certain platforms, such as Exchange Online, mandate TLS 1.2 for mail flow.
  • IPv6 Exception: TLS is crucial for deliverability when sending over IPv6.
  • Authentication Importance: Deliverability is more directly influenced by proper SPF, DKIM, and DMARC configuration.
  • Potential Future Impact: Major email providers like Google might factor TLS into email ranking in the future, mirroring web practices.
  • TLS Version Management: Disabling older TLS versions may be necessary for security reasons.
  • Interoperability Challenges: Decisions must be made on how to handle SMTP peers that do not support TLS 1.2.
  • SMTP TLS Reporting Benefits: SMTP TLS Reporting can help detect man-in-the-middle attacks, indirectly supporting deliverability.

Key considerations

  • Security Prioritization: Prioritize implementing TLS to secure email content, regardless of immediate deliverability gains.
  • Holistic Approach: Adopt a comprehensive approach to deliverability that considers factors beyond TLS, such as authentication, sender reputation, and content quality.
  • Compliance Adherence: Ensure compliance with platform-specific TLS requirements, such as those imposed by Exchange Online.
  • Trend Monitoring: Stay informed about evolving mailbox provider policies regarding TLS and deliverability.
  • Balancing Act: Weigh the benefits of using older TLS versions for compatibility against the security risks they pose.
  • Interoperability Strategy: Develop a strategy for handling SMTP peers that do not support TLS 1.2, balancing security and message delivery.
  • Reporting Evaluation: Assess the value of implementing SMTP TLS Reporting for improved security monitoring.

What email marketers say
11Marketer opinions

The use of TLS (Transport Layer Security) for email transmission is generally considered important for security and may have some impact on email deliverability and inbox placement. While TLS primarily encrypts email content during transit to prevent eavesdropping and tampering, some email providers may consider it a factor in sender reputation. Some experts suggest that not using TLS can negatively affect your sender reputation, as a significant portion of email traffic is now TLS encrypted. However, there are varying opinions on whether the lack of TLS directly impacts deliverability metrics. Some older versions of TLS should be disabled for security reasons, but you should send in clear text if there is a failure to negotiate a secure connection.

Key opinions

  • Encryption: TLS encrypts email content during transit, preventing eavesdropping and tampering.
  • Sender Reputation: Some email providers consider TLS as a factor in sender reputation, potentially impacting deliverability.
  • Security Best Practice: Using TLS signals to mailbox providers that the sender is committed to secure practices.
  • No Direct Impact: Some sources indicate that TLS doesn't directly influence deliverability metrics, but improves security.
  • TLS Versions: Older versions of TLS should be disabled for security reasons.
  • TLS Version Negotiation: Some experts recommend using clear text if there is a failure to negotiate a secure connection due to a lack of modern protocols.

Key considerations

  • Security vs. Deliverability: Balance the need for secure email transmission with potential impacts on deliverability.
  • Mailbox Provider Policies: Understand how different mailbox providers view TLS and its impact on sender reputation.
  • Configuration: Properly configure TLS on your outgoing mail server to prevent man-in-the-middle attacks.
  • Mitigation: If you can't negotiate TLS, you should drop back to plain-text
Marketer view

Email marketer from EmailGeeksForum.com says configuring TLS for your outgoing mail server is a must to secure your data and reduce the likelyhood of man-in-the-middle attacks. Using TLS helps maintain email security, which can positively influence deliverability.

March 2024 - EmailGeeksForum.com
Marketer view

Marketer from Email Geeks recommends using clear-text or TLSv1.2 and NOT pretending that v1/v1.1 are protecting your email in transit. They suggest to just go ahead and do `-TLSv1.1:-TLSv1.0:-SSLv3:-SSLv2` and drop back to plain-text if an attempt to negotiate opportunistic TLS via `STARTTLS` fails due to the remote not supporting `+TLSv1.2:+TLSv1.3`.

May 2024 - Email Geeks
Marketer view

Email marketer from StackOverflow shares that setting up TLS is really important to secure your email, without it anyone on your network may be able to see your password and email data. Using TLS helps maintain email security, which can positively influence deliverability.

August 2023 - StackOverflow
Marketer view

Email marketer from SMTP2GO highlights that TLS encrypts email communications to protect data during transit. Using TLS helps maintain email security, which can positively influence deliverability by signaling to mailbox providers that the sender is committed to secure practices.

October 2023 - SMTP2GO
Marketer view

Marketer from Email Geeks shares that you should disable TLSv1 and v1.1. If you can't make TLSv1.2 work, you should not pretend.

August 2021 - Email Geeks
Marketer view

Email marketer from Sendinblue emphasizes the importance of TLS encryption for secure email deliverability. It ensures the privacy and security of email communications during transmission, preventing unauthorized access. It may improve deliverability by meeting security standards expected by mailbox providers.

July 2024 - Sendinblue
Marketer view

Email marketer from Reddit explains that while TLS encrypts email content during transit, preventing eavesdropping, it doesn't directly influence deliverability metrics like inbox placement. However, some ISPs may view TLS usage as a positive signal, subtly improving reputation.

July 2024 - Reddit
Marketer view

Marketer from Email Geeks shares that it's absurd to question using TLS, as it requires basically zero effort for Opportunistic TLS. Not using TLS outbound looks bad and someone out there might use the data as a signal. Something like 85-90% of the world's email arrives to Gmail via TLS so you don't want to be an outlier.

October 2024 - Email Geeks
Marketer view

Email marketer from PrivacyMatters.com explains that configuring TLS for your outgoing mail server is a must to secure your data and reduce the likelyhood of man-in-the-middle attacks. Using TLS helps maintain email security, which can positively influence deliverability.

March 2023 - PrivacyMatters.com
Marketer view

Email marketer from SparkPost states that while TLS is essential for securing email transmission and protecting data, the lack of TLS doesn't necessarily affect the deliverability. However, they also mention that its absence might negatively affect the sending reputation of an email sender.

February 2025 - SparkPost
Marketer view

Email marketer from Mailjet explains that TLS encrypts the connection between mail servers to protect the contents of emails during transmission. It prevents eavesdropping and tampering. While it primarily addresses security, some email providers may consider it a factor in reputation and deliverability.

October 2022 - Mailjet

What the experts say
8Expert opinions

Experts offer varied perspectives on TLS and its impact on email deliverability. While TLS encrypts email content, its direct impact on deliverability isn't always clear. Some suggest it's primarily a security measure, while others note potential benefits in avoiding warnings or aligning with future practices of major email providers like Google. Government policies emphasize STARTTLS without specifying TLS versions for email. Interoperability issues with SMTP peers that don't support TLS 1.2 require choices between using lower TLS versions, refusing transfer, or sending in plain text. TLS configuration is not essential if SPF, DKIM and DMARC records are in place. SMTP TLS reporting helps catch MITM attacks.

Key opinions

  • Encryption Focus: TLS primarily addresses email content encryption for security.
  • Limited Direct Impact: Direct deliverability benefits of TLS are not clearly defined.
  • IPv6 Exception: TLS is crucial for deliverability when sending over IPv6.
  • Future Considerations: Google might eventually factor TLS into email ranking, mirroring web practices.
  • Government Stance: US policy favors STARTTLS without version requirements for email.
  • SMTP Interoperability: Choices needed when dealing with SMTP peers lacking TLS 1.2 support.
  • Importance: Encryption of your email communication is important but not essential to reaching the inbox.
  • Catch MITM attacks: SMTP TLS reporting helps catch MITM attacks.

Key considerations

  • Prioritize Security: Implement TLS to secure email content regardless of immediate deliverability boosts.
  • Monitor Trends: Stay updated on how mailbox providers evolve their treatment of TLS.
  • Address Interoperability: Plan for handling SMTP peers without TLS 1.2 support based on business needs.
  • Evaluate SMTP TLS reporting: Evaluate if SMTP TLS reporting is required for your platform.
Expert view

Expert from Email Geeks says Google has been strongly in favor of TLS for web traffic and will derank you if you’re not using good TLS. They may do something similar with email in the future.

May 2021 - Email Geeks
Expert view

Expert from Word to the Wise shares that one of the benefits of SMTP TLS Reporting is that it helps catch MITM attacks. If the TLS is broken, the receiving server may be able to tell you that something is wrong, which could help with deliverability.

May 2024 - Word to the Wise
Expert view

Expert from Email Geeks mentions that if there’s a choice between TLS 1.1 and clear text, you need to decide which you prefer, if you’re sending to a server that doesn’t speak 1.2 and your client is configured to refuse 1.1 that’s where you are.

May 2022 - Email Geeks
Expert view

Expert from Email Geeks explains that you have three choices when interoperating with an SMTP peer that doesn’t support TLS 1.2: use a transport with TLS 1.1 or below, refuse to transfer the mail, or send the mail plain text over an unencrypted transport.

March 2024 - Email Geeks
Expert view

Expert from Email Geeks shares that there's no real deliverability benefit to TLS, other than avoiding the red locks and encryption warnings.

January 2025 - Email Geeks
Expert view

Expert from Email Geeks explains that TLS isn’t really a deliverability issue, unless you’re sending over IPv6, in which case you should use TLS.

October 2024 - Email Geeks
Expert view

Expert from Email Geeks points out that US government policy is for STARTTLS and there isn’t any requirement for which TLS version to use. They’re very clear that 1.2 or 1.3 is required for government websites, but they just want something for email. Recommending to review Binding Operational Directive: <https://www.cisa.gov/news-events/directives/binding-operational-directive-18-01>

November 2022 - Email Geeks
Expert view

Expert from SpamResource shares that the encryption of your email communication is important but not essential to reaching the inbox. It does not affect deliverability as long as the SPF, DKIM and DMARC records are appropriately configured.

October 2021 - SpamResource

What the documentation says
3Technical articles

Technical documentation highlights the importance of TLS for securing email communications, but its direct impact on deliverability is nuanced. Microsoft Exchange Online requires TLS 1.2, making it essential for mail flow within that ecosystem. RFC documents TLS as a means of providing confidentiality and integrity protection for SMTP connections, but it doesn't guarantee message delivery. NIST provides guidelines for configuring TLS to secure data communications, emphasizing its role in protecting data confidentiality and integrity, but, similarly, it does not guarantee message delivery. Therefore, while TLS is crucial for secure and compliant email transmission, it doesn't inherently ensure inbox placement.

Key findings

  • Exchange Requirement: Exchange Online mandates TLS 1.2 for connections, ensuring basic mail flow.
  • Security Focus: TLS primarily secures email transmission by providing confidentiality and integrity protection.
  • No Delivery Guarantee: TLS implementation doesn't guarantee email delivery or inbox placement.

Key considerations

  • Compliance: Ensure compliance with platform-specific TLS requirements like those of Exchange Online.
  • Security Best Practices: Implement TLS to safeguard email content during transmission, regardless of direct deliverability impact.
  • Holistic Approach: Recognize that deliverability depends on factors beyond TLS, such as sender reputation, authentication, and content quality.
Technical article

Documentation from RFC details how a SMTP connection can be secured with Transport Layer Security (TLS) to provide confidentiality and integrity protection. Although its implementation is very import for protecting data across networks it does not guarantee delivery of messages.

December 2023 - RFC 3207
Technical article

Documentation from NIST provides guidance for configuring TLS (Transport Layer Security) server software. This documentation focuses on protocols, key exchange, and digital signatures, with the primary goal of securing communication and protecting data confidentiality and integrity. Although this will help protect data across networks it does not guarantee delivery of messages.

April 2021 - NIST
Technical article

Documentation from Microsoft Learn details that Exchange Online requires TLS 1.2 for connections. While not directly stated as impacting deliverability, failure to meet this requirement will prevent mail flow. Therefore, it indirectly impacts deliverability by ensuring messages can be transmitted in the first place.

December 2022 - Microsoft Learn