TLS 1.2 explained: Why it still matters for secure communications now

Transport Layer Security (TLS) 1.2 is one of the most widely deployed encryption protocols on the internet. It protects data exchanged between servers, securing everything from web browsing and APIs to email.

Even though TLS 1.3 is the latest version of the protocol, TLS 1.2 remains the most commonly used. It continues to underpin business-critical systems worldwide, supporting secure operations on a massive scale.

If your company handles sensitive information or sends customer and employee data over email, TLS 1.2 continues to play an essential role in maintaining confidentiality, preventing tampering, and ensuring trust.

The evolution from SSL to TLS 1.2

TLS didn’t appear on its own. It was designed as a response to weaknesses in Secure Sockets Layer (SSL), the earlier protocol used to protect online communication. Understanding this progression helps clarify why TLS 1.2 became the global baseline for secure data transfer.

SSL 3.0 was widely used in the early days of the internet but suffered from a major security issue found in 2014, Padding Oracle on Downgraded Legacy Encryption (POODLE). Over time, attacks demonstrated that SSL couldn’t provide the security modern systems required. As a result, version 3.0 was fully deprecated in June 2015 and shouldn’t be used today.

TLS 1.0 and, later, TLS 1.1 were introduced in 1999 and 2006 as modest security improvements to SSL. While they addressed some weaknesses, they still had several issues, with TLS 1.1 also never gaining widespread adoption. The Internet Engineering Task Force (IETF) has formally deprecated their use as of 2021.

TLS 1.2, released in 2008, marked a significant step forward. It introduced stronger encryption, fixed vulnerabilities, and enhanced performance. These improvements established TLS 1.2 as the recommended minimum for secure communication and ensured its broad adoption across browsers, servers, applications, and email environments.

TLS 1.3 arrived in 2018 with enhanced security, better speed, and the removal of outdated algorithms. Adoption continues to grow, but many systems still require TLS 1.2. As a result, both versions coexist today.

Why organizations should still care about TLS 1.2

TLS 1.3 brings important benefits, but TLS 1.2 remains essential for compatibility and operational stability.

Broad adoption and compatibility across systems

TLS 1.2 is supported by most mainstream browsers, operating systems, and application platforms in use today. Beyond that, it’s commonly built into IoT devices, embedded systems, and mobile applications.

Because systems evolve at different speeds, there are still many that can’t yet complete a TLS 1.3 handshake. Many older environments, external services, and third-party products still depend on TLS 1.2 for normal functionality.

Maintaining user trust through stable, secure connections

A secure connection depends on a successful TLS handshake. If a TLS 1.3 handshake fails, the connection can’t be established, which can affect user trust. Broken pages and non-delivered emails lead users to question whether your service is stable or secure. Supporting TLS 1.2 ensures connections remain stable for all users, not just those on the latest systems.

Meeting compliance and regulatory requirements

Many regulations and industry frameworks explicitly require TLS 1.2 at a minimum. These include standards covering financial data, health information, and government systems.

Businesses that continue using deprecated versions of TLS risk non-compliance penalties, increased exposure to attackers, and significant damage to brand reputation. Supporting TLS 1.2 ensures alignment with modern security expectations.

TLS 1.2 encryption and security features

TLS 1.2 introduced several improvements that strengthened secure communication across networks. Its key features include:

Stronger hashing and signature algorithms

TLS 1.2 moved away from the older MD5 and SHA-1 combination used in earlier versions. It was replaced with stronger hash algorithms – such as SHA-256 and SHA-384. This reduces reliance on outdated functions and provides better protection against tampering.

Introduction of modern AES cipher suites

TLS 1.2 introduced Advanced Encryption Standard (AES) cipher suites that support 128-bit and 256-bit keys. These deliver robust encryption for data in transit and enhance overall security.

Support for authenticated encryption

The protocol expanded support for authenticated encryption with associated data (AEAD) cipher suites. Modes such as GCM provide stronger security.

Improved client–server negotiation

Clients and servers can indicate which hash and signature algorithms they accept, giving both sides more flexibility and stronger security. This helps maintain compatibility while reducing the risks linked to older, less secure algorithms.

These additions helped TLS 1.2 remain relevant more than a decade after its introduction.

TLS 1.2 and email security

TLS 1.2 plays a critical role in email security. TLS uses a certificate to encrypt the connection between email servers so messages remain private while in transit. When both sending and receiving servers support TLS, the contents of the email are protected from interception and tampering.

As part of ongoing efforts to strengthen this encryption method, upcoming changes will shorten how long TLS certificates can remain valid.

Updated certificate lifetime schedule

The maximum lifetime for TLS certificates will continue to shorten over the next several years. Here is what to expect:

• The current limit of 398 days remains in place until March 15, 2026.
• On March 15, 2026, the maximum certificate lifetime will drop to 200 days.
• One year later, on March 15, 2027, it will be reduced again to 100 days.
• By March 15, 2029, the maximum lifetime will fall to just 47 days.

How MTA-STS and TLS-RPT strengthen TLS 1.2

Mail Transfer Agent Strict Transport Security (MTA-STS) adds a layer of enforcement to TLS. Domains can publish a policy stating that encrypted connections are expected. If a secure connection can’t be established, the message isn’t delivered.

TLS Reporting (TLS-RPT) works alongside MTA-STS to provide visibility into encrypted email delivery issues. Domain owners publish a reporting address in the DNS, and receiving email servers send daily reports on delivery failures. These reports specify the IP addresses involved, the type of issue, the TLS policy, and the date and time the failure occurred.

These reports help companies identify misconfigurations, improve email security, enhance regulatory compliance, and build customer trust.

By combining TLS 1.2, MTA-STS, and TLS-RPT, organizations significantly reduce the risk of interception and gain clear insight into TLS issues. This strengthens security and ensures you can track and address problems as they emerge.

If you want help implementing or managing MTA-STS and TLS-RPT, Sendmarc makes the process simple. We help you publish your policies, monitor encrypted email delivery, provide visibility into successful TLS connections, and support you through ongoing maintenance.

Book a demo to see how Sendmarc helps you deploy MTA-STS, interpret TLS-RPT reports, and strengthen your overall email security.