There is a tool called testssl.sh - a free command line tool which checks a server's service on any port for the support of TLS/SSL ciphers, protocols as well as recent cryptographic flaws and more. Very extensive.
$ ./testssl.sh --starttls smtp myrelay.example.org:25 $ ./testssl.sh www.example.org
Or run some simpler tests:
$ openssl s_client -cipher 'DHE' -starttls smtp -crlf -connect myrelay.example.org:25
An older blog entry: SWAKS - Swiss Army Knife SMTP, the all-purpose SMTP transaction tester
2020/01/25 Send an email to
auth-results@verifier.port25.comand receive back an informative reply about message handling: SPF, DKIM, iprev, SpamAssassin, DNS.
2020/01/25 Visit mail-tester.com for another flavour of email tester for spamminess.
2022/06/11 Authentication Checker
2022/06/11 mx toolbox
2024/01/26 about my email