Check a Domain's Inbound Email Servers for TLS Support

Domain to Check:

Please type the text seen in the image, below, into the "Security Code" box.

Security Code:

The security code is the text that you see in the image, above. Use of this code helps us prevent abuse of this form by automated programs.


TLS, short for Transport Layer Security, is a protocol used for establishing a secure connection between two computers across the Internet. As an email provider we give our clients the best of security options, and TLS is a very important security tool. Our system gives our users the option to use TLS or SSL when connecting their email client (Outlook, Apple Mail, etc) to our incoming and outgoing servers for the purpose of encrypting the connection itself.

Read: SMTP TLS: All About Secure Email Delivery over TLS

Enforced use of SMTP TLS is one of several methods that LuxSci SecureLine email encryption can use to ensure secure email delivery. See: How SecureLine Works. In particular, LuxSci SecureLine allows you to leverage TLS for secure email delivery, if you choose, via:

  • Dynamically determining what recipients support TLS, so you do not have to pre-configure anything.
  • Automatic fall-back to other email encryption modes when TLS is not available, so you don't have to configure anything.
  • Allowing you to optionally specify which domains or recipients are OK or not OK for TLS-Only email delivery.
  • Allowing you to optionally NOT deliver email to people to do not support TLS, instead of using other encryption methods (good for email marketing in a compliance context).
  • Access to an API where you can check domains for their TLS support before you ever send email messages.
  • Access to an API for sending secure email messages, in case you prefer to not use SMTP directly.

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About the TLS Checker Tool

This TLS Checker is solely concerned with TLS in relation to the recipient of the email you send (SMTP); specifically whether the recipient's inbound email servers support "Opportunistic TLS". When our servers connect to the recipient's servers, they check to determine if TLS encryption is available. (See: How to Tell Who Supports TLS for Email Transmission).

By entering the domain of someone's email address and clicking on the "Check for TLS Support" button, you can determine if their inbound email servers are capable of using TLS. If you are using an email provider that enforces the same level of security that we do here at LuxSci then email sent to users in that domain should be automatically sent over an encrypted connection. This will make it so that your email communications cannot be eavesdropped upon.

Note that secure server-to-server communications should only use TLS v1.0+ (and not SSL v3.0) and should use strong ciphers (see NIST 800-52r1). This tool indicates domains that have TLS support but which are configured poorly so that they do not provide the option to use this level of encryption.

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