Best MTA-STS Providers to Secure Your Emails

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Looking for reliable MTA-STS providers? Discover the best hosted MTA-STS services that help enforce TLS encryption, and protect against SMTP attacks.

by Milena Baghdasaryan

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Best MTA-STS Providers to Secure Your Emails
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MTA-STS (Mail Transfer Agent Strict Transport Security) is a security protocol that enforces encrypted email delivery between mail servers using TLS. It ensures that messages sent to your domain are delivered only over secure channels. If encryption can’t be established, delivery is blocked entirely.

Originally championed by Google in 2019, MTA-STS has since become a critical layer of email security, especially for organizations concerned about downgrade attacks and SMTP-based interception.

Today, most MTA-STS policies are hosted by third-party providers. So, how do you choose the right one? Below, we highlight top MTA-STS providers that offer reliable hosting, automation, and reporting features to help secure your domain.

Key Takeaways

  • MTA-STS helps enforce TLS encryption for inbound email delivery.
  • It protects against MITM attacks, solves SMTP security issues, and makes encryption in transit mandatory.
  • MTA-STS implementation remains quite low because of technical difficulties. However, hosted MTA-STS services can help overcome these challenges.
  • Some of the best MTA-STS providers in the market include PowerDMARC, URIports, Mailhardener, and OnDMARC.
  • Which provider you should choose depends on several factors, including budgetary considerations, scope of features, ease of use, etc.

Why Do Businesses Need MTA-STS?

MTA-STS enforces encrypted SMTP delivery using TLS and prevents downgrade attacks. The protocol offers many benefits, including:

Enforcing Policy-Based TLS Monitoring 

MTA-STS protects against man-in-the-middle (MITM) attacks like SMTP downgrade and DNS spoofing by enforcing the use of valid, encrypted TLS connections.

SMTP Security Enforcement

MTA-STS mitigates certain SMTP vulnerabilities by ensuring that emails are only delivered to servers supporting TLS encryption. If the recipient server doesn’t support encryption or presents an invalid certificate, the message will not be delivered, avoiding insecure fallback.

Secure Transport for Email

MTA-STS ensures that emails are transmitted securely over TLS, helping protect message data from interception or tampering while in transit. This reduces the risk of unauthorized access during SMTP delivery but does not provide end-to-end encryption.

Enforced TLS Encryption for SMTP

When both sender and recipient domains support MTA-STS, encryption during SMTP transmission becomes mandatory. This prevents messages from being sent over plaintext or downgraded connections. However, note that MTA-STS only protects email while in transit, not after delivery or at rest. 

Top MTA-STS Providers

Here are the five largest MTA-STS providers.

1. PowerDMARC

PowerDMARC stands out as one of the top MTA-STS providers, offering a smooth and user-friendly deployment experience. PowerDMARC’s hosted MTA-STS feature enables you to automate MTA-STS setup, manage MTA-STS policy files & enable TLS-RPT for your domain directly within the PowerDMARC portal. This decreases manual effort, ensures error-free configuration, and requires no technical knowledge. 

Pros

  • Offers a free MTA-STS record checker and validation tool
  • Handles policy web hosting and TLS certificate maintenance.
  • Helps deploy MTA-STS with minimal setup or manual intervention.
  • RFC-Compliant and TLS-Ready
  • Supports the latest TLS standards and aligns with RFC guidelines
  • Enables direct policy updates via dashboard—no DNS edits required.
  • Provides expert guidance and detailed resources

2. URIports

URIports provides a hosted MTA-STS service to automate the policy generation and help you avoid common MTA-STS configuration problems. URIports’ hosted MTA-STS is included at no additional charge in several subscription plans. The service helps you achieve error-free DNS configuration while also taking care of the HTTPS certificates. 

Pros

  • Provides a free validation tool to check if your domain is MTA-STS ready.
  • URIports’ hosted MTA-STS service is included at no additional cost in their Pebble Plus, Stone, Mountain, and Himalaya subscriptions.
  • All you need to do is add two CNAME records to your domain’s DNS; nothing more is required from your side. URIports will then publish an RFC-compliant MTA-STS policy on your behalf. 
  • It regularly validates your policy and overall email setup.

3. Mailhardener 

Mailhardener provides a hosted MTA-STS service that includes policy hosting, certificate management, and automatic renewal. The service also updates the ID value automatically when policy changes occur. Users can configure and modify their MTA-STS policies through the Mailhardener dashboard, without needing to manually edit DNS records or use technical tools.

Pros

  • Mailhardener’s hosted MTA-STS is RFC-compliant and supports the most recent TLS standards.
  • If you want to self-host MTA-STS yourself, you can still leverage Mailhardener to aggregate and process your SMTP TLS reports.
  • Takes care of hosting and maintaining the web server and certificate.
  • Their hosted MTA-STS is available immediately to Mailhardener customers.

4. OnDMARC 

 

Red Sift OnDMARC’s MTA-STS feature hosts the policy file and manages SSL certificate renewals. It also detects policy violations through detailed TLS reports, helping you identify suspicious activity early. These reports offer insights into email delivery volume and encryption status, guiding you toward achieving MTA-STS enforce mode to secure your inbound email.

Pros

  • Through its Investigate tool, OnDMARC provides a real-time check on your email sending service in seconds and tells you if your MTA-STS is set up correctly. 
  • Their service enables you to obtain granular details and insights into the reasons for a domain’s success or failure (e.g., missing or expired certificate).
  • OnDMARC is a well-reputed name in the market. 

Bonus: Providers Offering MTA-STS Record Validation

Apart from the top 4 MTA-STS providers, here are some additional providers that offer MTA-STS record validation:

  • dmarcian: You need to log in to your dmarcian account to use their MTS-STS Inspector Tool.
  • MxToolbox: Their MTA-STS lookup tool checks a domain or hostname for an MTA-STS DNS TXT record and a valid MTA-STS Policy.
  • Thexyz: Their MTA-STS check tool performs a quick lookup to check your MTA-STS TXT record, TLS reporting, and other configurations.
  • Skysnag: Their MTA-STS checker helps ensure your emails are transmitted safely and securely with TLS encryption.

FAQs

What is MTA-STS?

MTA-STS is an email authentication protocol that ensures the secure transmission of emails over an encrypted SMTP connection.

What benefits does it offer?

MTA-STS helps solve major SMTP security problems, such as expired TLS certificates and a lack of support for secure protocols. It boosts security, enhances compliance, and reduces vulnerabilities and security gaps. 

Can I configure MTA-STS manually by myself?

While you can configure MTA-STS by yourself, it’s not recommended, especially if you lack the necessary technical know-how. You can benefit from hosted MTA-STS services for enhanced ease and convenience. 

What are the best MTA-STS providers?

PowerDMARC, URIports, Mailhardener, and OnDMARC are some of the top MTA-STS providers in the market.  

What should I pay attention to when choosing an MTA-STS provider?

You should consider pricing, ease of use, scalability, scope of features, user reviews, and other relevant factors. 

Why should MTA-STS users monitor TLS reports?

MTA-STS users should monitor TLS reports to detect and act upon potential issues related to email delivery to their domains.

Summing Up 

MTA-STS adoption has grown steadily in recent years, but overall implementation remains low across many industries and regions. One major barrier is the complexity involved in setting up and maintaining MTA-STS correctly.

Fortunately, several providers now offer hosted MTA-STS solutions along with built-in MTA-STS checkers, making it easier to deploy the protocol and validate your configuration with confidence.

If you need help configuring advanced email authentication like MTA-STS, TLS-RPT, and more, contact PowerDMARC today. Our dedicated team of experts and real human support has helped thousands of organizations implement MTA-STS for their mission-critical domains. Book a demo to learn more! 

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