Question 1

What is STARTTLS?

Accepted Answer

STARTTLS is the mechanism an SMTP mail server uses to upgrade a plain connection to an encrypted TLS one. If your mail server does not offer STARTTLS, email sent to and from your domain can travel across the internet in plaintext, where it can be read or tampered with.

Question 2

How do I check if my mail server supports TLS?

Accepted Answer

You connect to the mail server on port 25, send an EHLO command, and look for a STARTTLS capability in the response. This checker does that automatically for every MX host of your domain and also verifies the TLS certificate is present and not expired.

Question 3

Why does TLS matter for deliverability?

Accepted Answer

Receiving providers treat a sender that cannot encrypt as a weak signal. Gmail and Microsoft expect TLS for most mail. A missing or expired certificate is a common, fixable reason mail gets down-ranked or flagged.

Question 4

Is this TLS checker free?

Accepted Answer

Yes. The check is free and does not require a signup. It runs a live connection to your mail servers, so results reflect the current state of your infrastructure.

Question 5

What if my domain has no MX records?

Accepted Answer

If there are no MX records, the checker falls back to the domain's own A record. If neither exists, it reports that there is no mail host to test.

TLS / STARTTLS checker

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