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What is MTA-STS? A detailed guide

What is MTA-STS, and why does email transport security matter?

Email is a primary method of business communication and often contains sensitive data. Without proper security, like Mail Transfer Agent Strict Transport Security (MTA-STS), emails can be intercepted, read, or altered during transit. This puts organizations at risk of data breaches, fraud, and compliance violations.

So, what is MTA-STS? MTA-STS is a type of transport security that ensures that messages are encrypted while traveling between email servers, reducing the risk of Man-in-the-Middle (MitM) attacks and unauthorized access. It helps build confidence between sending and receiving domains by ensuring that messages arrive safely and intact. It is also closely related to Transport Layer Security Reporting (TLS-RPT), which provides reporting and visibility on the enforcement of this policy.

Want to strengthen your business’s email transport security?

Book a demo to see how Sendmarc helps protect your company’s domain.

What is MTA-STS, and what does it do?

MTA-STS is a security standard that tells other email servers your organization’s domain only accepts emails sent over encrypted connections using TLS. It prevents attackers from taking advantage of weaknesses often found in traditional email delivery, such as intercepting or modifying messages sent over unsecured channels.

By enforcing encrypted delivery, MTA-STS helps ensure that malicious actors can’t hijack or spy on email communications during transit – an important layer of protection for modern businesses.

What is MTA-STS in email, and how does it protect companies?

MTA-STS works by publishing a policy that instructs sending email servers to:

Only deliver emails to a domain if a secure (TLS-encrypted) connection can be established (with the correct policy)
Verify that the server’s TLS certificate is valid
Based on the domain’s MTA-STS policy, an SMTP server might refuse to deliver an email if the required TLS security checks fail

This means that even if an attacker attempts to intercept or downgrade the connection, the email won’t be delivered unless the connection remains secure, protecting both the sender and the recipient.

What is MTA-STS, and what is its significance?

MTA-STS is a protocol that can help ensure that emails are only delivered to your organization’s domain if the sending server can establish a secure, encrypted connection (TLS) and validate its identity with a trusted certificate.

Why it matters:

MTA-STS closes security gaps left by older protocols such as STARTTLS, which can be downgraded or bypassed by attackers. By enforcing strict transport encryption, MTA-STS reduces the risk of email interception and strengthens trust in your business’s email infrastructure.

It also shows a commitment to strong cybersecurity practices – an important consideration for customers, partners, and regulators.

What is MTA-STS: MTA-STS explained simply

Think of sending an email like mailing a letter.

Without MTA-STS, your company’s letter could be opened or tampered with on its way to the recipient, and your organization wouldn’t even know.

With MTA-STS, your business’s letter is locked in a secure, tamper-proof box. It is only delivered if the path from sender to recipient can stay encrypted and safe. If the security can’t be guaranteed, the message isn’t delivered at all.

What is MTA-STS, and what are its benefits?

Prevents interception: Enforces encryption to stop attackers from reading or tampering with emails in transit
Reduces downgrade attacks: Blocks attempts to force email delivery over unencrypted connections
Improves privacy: Protects sensitive company information while it travels between email servers
Boosts domain reputation: Shows others that your organization takes security seriously

Book a demo to discover how Sendmarc can help your business secure its domain and protect its communications.

What is MTA-STS, and when might your company encounter it?

MTA-STS is relevant if:

Your organization wants to secure inbound email delivery
Your business’s domain handles sensitive communications
Your company is in a regulated industry with strict data privacy standards
Your organization wants to stop attackers from abusing insecure email delivery

What is MTA-STS: FAQs

What does MTA-STS do?

MTA-STS enforces the encrypted, authenticated delivery of emails to your business’s domain and can block any messages sent over insecure connections.

What problem does MTA-STS solve?

MTA-STS solves the problem of attackers intercepting or tampering with emails in transit by requiring secure, encrypted transport.

How is MTA-STS related to email?

MTA-STS is an email security standard that requires that the path your company’s emails take between servers is secure, protecting messages while they’re in transit.

Do I need to understand TLS-RPT to use MTA-STS?

Transport Layer Security Reporting (TLS-RPT) doesn’t necessarily need to be understood to implement MTA-STS. TLS-RPT works with MTA-STS to send reports about encryption issues, helping your organization monitor and strengthen email security.

Who uses MTA-STS?

Businesses that care about secure, reliable email delivery, especially those handling sensitive or regulated data, use MTA-STS.

How does MTA-STS help protect me?

MTA-STS helps protect by ensuring only encrypted, authenticated connections are accepted when delivering email to your company’s domain, keeping its communications private and secure.

What is an MTA-STS record?

An MTA-STS record is a DNS record that tells other email servers your organization’s domain supports MTA-STS and points them to its published security policy.

Ready to secure your business’s email?

Book a demo and see how Sendmarc makes email transport security simple, effective, and reliable.