Why is outbound TLS important for email marketing?

Summary

Outbound TLS is considered essential for secure email marketing. It encrypts email traffic during transit, protecting sensitive data and preventing interception and data breaches. It also demonstrates a commitment to security, building trust with recipients and positively impacting sender reputation and deliverability. Failing to implement TLS can lead to warnings from email providers like Gmail. GDPR and similar regulations may also mandate TLS for email security. Implementation should extend beyond the email body to include CTA URLs and other resources. Opportunistic TLS is an option, but not as effective as requiring TLS connections. It is a standard practice, the lack of which can raise red flags.

Key findings

  • Encryption: TLS encrypts email traffic, preventing unauthorized access to sensitive information during transit.
  • Reputation & Trust: Implementing TLS builds trust with recipients and improves sender reputation, enhancing deliverability.
  • Regulatory Compliance: TLS helps comply with data protection regulations like GDPR, which mandate security measures for personal data.
  • Industry Standard: TLS is considered an industry-standard security practice for email communication.
  • Gmail Warnings: Gmail displays warnings on messages without TLS, negatively impacting user perception.

Key considerations

  • Scope of TLS: TLS should be implemented not only for email content but also for CTAs and other embedded resources.
  • Enforced vs. Opportunistic: While Opportunistic TLS is better than none, requiring TLS connections provides superior security by preventing fallback to plain text.
  • OpenSSL: OpenSSL can assist with enabling TLS and ensure you are up to date with the latest versions.

What email marketers say
11Marketer opinions

Outbound TLS is considered essential for modern email marketing. It encrypts email traffic in transit, protecting sensitive data from interception and data breaches. It is also a demonstration of commitment to security and builds trust with recipients, positively impacting sender reputation and deliverability. GDPR may also require TLS for email security. Implementation should extend beyond the main email content to include CTA URLs and other remote resources. It encrypts email traffic from sending to receiving server, preventing content sniffing. Without TLS, SMTP transactions expose sensitive data in plain text.

Key opinions

  • Encryption: TLS encrypts email traffic during transit, preventing eavesdropping and protecting sensitive information.
  • Trust & Reputation: Implementing TLS builds trust with recipients and enhances sender reputation, which can improve deliverability.
  • Security Compliance: GDPR and other regulations may require TLS to ensure the security of personal data transmitted via email.
  • Best Practice: TLS is now considered a standard best practice, and its absence can raise suspicion.

Key considerations

  • Scope of Implementation: TLS should be implemented not only for email content but also for CTA URLs and any other remote resources (images, CSS, etc.)
  • Opportunistic vs. Enforced: Opportunistic TLS is better than nothing but isn't as secure as enforced TLS as it falls back to plain text if the receiving server doesn't support TLS. If possible enforce TLS.
Marketer view

Marketer from Email Geeks states outbound TLS shouldn't even be optional anymore.

June 2021 - Email Geeks
Marketer view

Marketer from Email Geeks advises that TLS should also be implemented for CTA URLs and any other remote resources like CSS and images.

September 2022 - Email Geeks
Marketer view

Email marketer from Reddit answers that TLS builds trust and reputation for your email domain. It is essentially a trust indicator.

May 2021 - Reddit
Marketer view

Email marketer from Reddit answers that TLS is a standard practice and is essential if you want to ensure your email doesn't look sus.

September 2024 - Reddit
Marketer view

Marketer from Email Geeks explains outbound TLS encrypts email traffic from sending to receiving server, preventing content sniffing. Without TLS, SMTP transactions expose sensitive data in plain text.

July 2024 - Email Geeks
Marketer view

Marketer from Email Geeks explains that outbound TLS may not have an immediate impact on deliverability, but it is likely considered by reputation and anti-threat systems. Furthermore, under GDPR, enforcing security like outbound TLS is a requirement.

June 2022 - Email Geeks
Marketer view

Email marketer from Mailgun.com explains that TLS encrypts email in transit, protecting the content from being intercepted and read by malicious actors. It's crucial for maintaining the privacy and security of sensitive data.

May 2024 - Mailgun.com
Marketer view

Email marketer from SocketLabs.com shares that TLS establishes a secure connection and is a critical component for maintaining data integrity and preventing unauthorized access. It plays a role in building sender reputation and deliverability.

March 2022 - SocketLabs.com
Marketer view

Email marketer from SparkPost.com highlights that TLS ensures secure communication between email servers, preventing eavesdropping and data breaches. Using TLS demonstrates a commitment to security and builds trust with recipients.

December 2024 - SparkPost.com
Marketer view

Email marketer from StackOverflow mentions that TLS makes sure that people cannot look at sensitive information such as credit card numbers during sending.

March 2023 - StackOverflow
Marketer view

Email marketer from Reddit answers that TLS provides encryption of email during transit so people can't snoop on the messages

December 2024 - Reddit

What the experts say
4Expert opinions

Experts emphasize the necessity of outbound TLS for email marketing due to the secure channel it provides, protecting sensitive information from interception and contributing to sender reputation. A lack of TLS can result in warnings from email providers like Gmail. Opportunistic TLS is a potential solution, but falls back to plain text if TLS isn't supported by the receiving server.

Key opinions

  • TLS is Essential: Outbound TLS is considered absolutely necessary for secure email communication.
  • Gmail Warnings: Gmail displays warnings for messages sent without TLS, which can negatively impact recipient trust.
  • Reputation Boost: Using TLS demonstrates a commitment to security, contributing positively to sender reputation.
  • Data Integrity: TLS helps maintain the integrity of email data during transmission.

Key considerations

  • Opportunistic TLS Limitations: While Opportunistic TLS is better than nothing, it's not ideal as it defaults to plain text if the receiving server doesn't support TLS.
Expert view

Expert from Email Geeks states that outbound TLS is absolutely necessary.

January 2022 - Email Geeks
Expert view

Expert from Wordtothewise.com explains that TLS provides a secure channel for email communication, protecting sensitive information from interception. It contributes to sender reputation by demonstrating a commitment to security and helps maintain data integrity.

November 2022 - Wordtothewise.com
Expert view

Expert from Spamresource explains that Opportunistic TLS allows a sending server to attempt to negotiate a TLS connection with a receiving server. If the receiving server supports TLS, the connection is encrypted; otherwise, the email is sent in plain text. This is better than nothing, but not ideal.

July 2023 - Spamresource.com
Expert view

Expert from Email Geeks explains that Gmail adds a warning to messages lacking TLS.

January 2024 - Email Geeks

What the documentation says
4Technical articles

Technical documentation indicates that TLS provides communications privacy and data integrity through encryption. It secures SMTP mail flow, protecting communications with trusted partners. TLS can be implemented in various environments, like Java, to protect web communications. OpenSSL offers resources to implement different TLS versions.

Key findings

  • Privacy and Integrity: TLS secures communications by providing both privacy and data integrity.
  • Secure Mail Flow: Enabling TLS secures SMTP mail flow, especially with trusted business partners.
  • Versatile Implementation: TLS can be implemented in a variety of environments, including Java applications and web communications.
  • Version Support: OpenSSL provides documentation on supported TLS versions and their implementation.

Key considerations

Technical article

Documentation from Microsoft Learn explains that enabling TLS for SMTP helps secure mail flow between your Microsoft 365 or Office 365 organization and your trusted business partners. It's a way to encrypt email communications.

November 2022 - Microsoft Learn
Technical article

Documentation from RFC5246 explains that The Transport Layer Security (TLS) Protocol provides communications privacy and data integrity. The protocol is composed of two layers: the TLS Record Protocol and the TLS Handshake Protocol.

February 2025 - RFC5246
Technical article

Documentation from OpenSSL explains the different versions of TLS that are supported and how to implement them.

April 2023 - OpenSSL.org
Technical article

Documentation from Oracle.com explains how you can use TLS to protect communication in java. It enables secure, reliable, and efficient communication to transfer information across the web.

November 2023 - Oracle.com