STARTTLS, TLS & DANE check
How secure is the transport encryption of your mail server? The MX Server Tester checks STARTTLS, TLS versions, certificates, DANE/TLSA and perfect forward secrecy – the points that decide about delivery and confidentiality of your emails.
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Register freeTest Mail Server Security
Enter a domain to check its mail servers for STARTTLS support, TLS versions, certificate validity, and security features like Perfect Forward Secrecy.
How it works
1. Enter domain
Enter the domain whose MX servers you want to check.
2. Test connections
The tester opens SMTP connections and negotiates TLS.
3. Cached result
The result is cached briefly and shareable via link.
Features in detail
STARTTLS detection
Check whether and how STARTTLS is offered on ports 25/587/465.
TLS versions
Which TLS versions and cipher suites does your server support?
DANE check
TLSA records and DANE configuration are validated directly.
PFS
Perfect forward secrecy – protects past communication in case of key leaks.
Certificate analysis
Chain, expiry, SAN entries and validity in detail.
No account needed
Free and without registration.
Frequently asked questions
What is an MX record?
An MX record (Mail Exchanger) is a DNS entry defining which mail server accepts email for a domain. Without an MX record, no email reaches the domain.
Why is my email delivery failing?
Common causes: wrong or missing MX record, mail server offline, wrong priorities, missing SPF/DKIM/DMARC, or expired certificates. The MX test shows you instantly which one it is.
What does MX record priority mean?
The number before the mail server (e.g. 10 mail1.domain.de) defines the order: lower = tried first. If the primary fails, the next priority takes over — that is your failover.
How do I check if my mail server is offline?
The MX test connects live to your mail server (port 25/465/587), checks STARTTLS, TLS version, certificate and responds within seconds.
What is DANE?
DANE (RFC 6698) anchors TLS certificates via TLSA records in DNS, protecting against forged certificates. The MX tester checks whether your DANE setup is correct.
Why is STARTTLS important?
STARTTLS encrypts transport between mail servers. Without STARTTLS, emails travel the network in plaintext – a privacy and security risk.
Will my server be flagged as spam source by the test?
No. The test only opens a regular SMTP connection without sending emails.