TLS (Transport Layer Security) is the protocol that replaced SSL. It was introduced in 1999 as an upgrade to SSL 3.0 and has been revised several times since: - TLS 1.0 (1999) — the first TLS version; deprecated in 2021. - TLS 1.1 (2006) — added protections against certain attacks; deprecated in 2021. - TLS 1.2 (2008) — introduced stronger, configurable cipher suites and is still widely deployed. - TLS 1.3 (2018) — removed obsolete cryptography, made the handshake faster, and is the current best practice. TLS does the same job SSL was meant to do — establish an encrypted, tamper-evident channel between two endpoints — but with modern cryptography and the accumulated fixes of two decades. It

SSL vs TLS: what's the difference for email?

SSL and TLS are two generations of the same idea: a protocol that encrypts data as it travels between two machines. TLS (Transport Layer Security) is the modern, secure successor to SSL (Secure Sockets Layer), which is now deprecated and unsafe to use. When people say "SSL" today — including "SSL certificate" — they almost always mean TLS.

Quick Takeaways

TLS is the direct successor to SSL; they are not two competing protocols but old and new versions of one.
Every version of SSL (2.0 and 3.0) is deprecated and insecure. SSL 3.0 was broken by the POODLE attack.
TLS 1.2 and TLS 1.3 are the versions in active use. TLS 1.0 and 1.1 were formally deprecated in 2021.
For email, TLS encrypts messages in transit between mail servers and between your mail client and server.
TLS protects the connection, not the sender's identity — that is the job of SPF, DKIM, and DMARC.
"SSL certificate" is a common misnomer; the certificates used today are validated over TLS.

What is SSL?

SSL (Secure Sockets Layer) was the original protocol for encrypting network connections, developed by Netscape in the mid-1990s. It went through two public versions: SSL 2.0 and SSL 3.0. Both are now considered broken. SSL 2.0 had fundamental design flaws, and SSL 3.0 was compromised by the POODLE attack, which let an attacker on the network decrypt parts of a supposedly private session.

Because of these weaknesses, every mainstream browser, mail server, and operating system has disabled SSL. The name survived in everyday language — you still hear "SSL certificate" and "SSL connection" — but the underlying handshake almost never uses the SSL protocol anymore.

What is TLS?

TLS (Transport Layer Security) is the protocol that replaced SSL. It was introduced in 1999 as an upgrade to SSL 3.0 and has been revised several times since:

TLS 1.0 (1999) — the first TLS version; deprecated in 2021.
TLS 1.1 (2006) — added protections against certain attacks; deprecated in 2021.
TLS 1.2 (2008) — introduced stronger, configurable cipher suites and is still widely deployed.
TLS 1.3 (2018) — removed obsolete cryptography, made the handshake faster, and is the current best practice.

TLS does the same job SSL was meant to do — establish an encrypted, tamper-evident channel between two endpoints — but with modern cryptography and the accumulated fixes of two decades. It underpins HTTPS on the web (see what HTTPS is) and secures mail transport for SMTP, IMAP, and POP.

What is the difference between SSL and TLS?

The practical difference is straightforward: SSL is the deprecated ancestor and TLS is the maintained standard you should actually use. They are not interchangeable options for a new setup — SSL is simply the old version you turn off.

A few concrete distinctions:

Security. SSL 2.0 and 3.0 have known, exploitable weaknesses. TLS 1.2 and 1.3 do not have equivalent breaks and receive ongoing scrutiny.
Handshake. TLS 1.3 streamlined the connection setup, reducing round trips and dropping insecure options that older SSL/TLS handshakes still negotiated.
Cipher support. TLS removed weak ciphers that SSL permitted, and TLS 1.3 restricts negotiation to a small set of strong algorithms.
Terminology. The certificates you buy are often called "SSL certificates," but they are protocol-agnostic — the same certificate works over TLS. The label is marketing habit, not a technical requirement.

For a deeper primer on each, see what SSL is and what TLS is.

How does TLS protect email?

Email uses TLS in two places. First, between mail servers: when your server hands a message to the recipient's server over SMTP, TLS can encrypt that hop so it cannot be read on the wire. Second, between you and your own mail provider: your desktop or phone client uses TLS when it sends mail (SMTP submission) and when it fetches mail (IMAP or POP).

There are two ways email negotiates TLS:

STARTTLS (opportunistic TLS). The connection starts in plaintext, then upgrades to TLS if both sides support it. This is common on submission port 587 and server-to-server port 25.
Implicit TLS. The connection is encrypted from the first byte, typically on port 465 for submission and 993/995 for IMAP/POP.

The catch with opportunistic STARTTLS is that an active attacker on the path can strip the upgrade and force the session back to plaintext. Standards like MTA-STS exist to close that gap by telling sending servers to require TLS for your domain and refuse to deliver if it is missing.

Does TLS replace SPF, DKIM, and DMARC?

No — and this is the most common misconception. TLS secures the pipe the email travels through. It says nothing about who actually sent the message. A phishing message can be delivered over a perfectly valid TLS connection.

Sender identity is a separate problem solved by email authentication:

SPF verifies which servers are allowed to send for your domain.
DKIM cryptographically signs the message so tampering is detectable.
DMARC ties SPF and DKIM to the visible From address and tells receivers what to do on failure.

TLS and authentication are complementary. You want both: TLS so nobody can read or alter mail in transit, and DMARC so nobody can spoof your domain in the first place.

Which TLS version should you use?

Use TLS 1.2 at a minimum, and prefer TLS 1.3 wherever your software and your correspondents support it. Disable SSL 2.0, SSL 3.0, TLS 1.0, and TLS 1.1 — these were formally deprecated and offer no benefit today beyond compatibility with systems that are themselves out of support.

Most modern mail servers and cloud email providers already default to TLS 1.2/1.3, so for many teams this is a matter of confirming the configuration rather than changing it.

Common issues with TLS for email

Mail is sent in plaintext even though TLS is "enabled"

Opportunistic STARTTLS silently falls back to plaintext if the handshake fails or is stripped. Enabling STARTTLS is not the same as requiring it. Publish an MTA-STS policy so sending servers enforce TLS for your domain, and monitor TLS reporting (TLS-RPT) to see when delivery happens without encryption.

An old device or app can't connect after a TLS upgrade

When you disable TLS 1.0/1.1, legacy printers, scanners, or line-of-business apps that only speak old protocols will fail to send. The fix is to update or replace the client, not to re-enable the deprecated protocol for everyone. Isolate the laggard on a dedicated relay if you truly cannot upgrade it.

Certificate name mismatch or expiry breaks the connection

TLS validates the server's certificate. If the certificate is expired, self-signed, or issued for a different hostname than the mail server presents, strict clients refuse the connection. Confirm the certificate matches the exact mail hostname (for example mail.example.com) and automate renewal so it never lapses.

"SSL error" messages that are really TLS problems

Because tools still label everything "SSL," an "SSL handshake failed" error usually points at a TLS negotiation issue — a version mismatch, an unsupported cipher, or a missing certificate chain. Check which TLS versions and ciphers both ends actually support before assuming the certificate is at fault.

Frequently asked questions

Is SSL still used anywhere? Rarely, and it should not be. Some tools and dashboards still say "SSL," but the actual connection is negotiated with TLS. Any endpoint genuinely running SSL 2.0 or 3.0 is a security risk that should be remediated.

Is an "SSL certificate" different from a "TLS certificate"? No. It is the same X.509 certificate. "SSL certificate" is a legacy name that stuck. The certificate works over whatever TLS version the client and server agree on.

Does TLS encrypt the whole email end to end? No. TLS encrypts each hop the message takes, but the message is decrypted at each mail server along the way. For end-to-end confidentiality you need message-level encryption such as S/MIME or PGP on top of TLS.

Do I still need DMARC if my email uses TLS? Yes. TLS protects the connection; it does not stop someone from forging your From address. Run a scan with the Email Security Score tool to see whether your domain is actually protected.

Palisade automates the authentication half of this picture — it monitors your SPF, DKIM, and DMARC records, flags gaps, and guides you to enforcement so that a TLS-encrypted message is also a verified one. Check where your domain stands with the free Email Security Score.