mastodon.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
The original server operated by the Mastodon gGmbH non-profit

Administered by:

Server stats:

380K
active users

Command Line Magic

openssl s_client -connect smtp.example.com:25 -starttls smtp # If you used to use telnet or netcat to test protocols, but are stumped by SSL/TLS connections. Try using openssl s_client with --starttls and the name of the protocol.