openssl s_client -quiet -crlf -starttls smtp -connect mail.example.com:25
openssl s_client -starttls smtp -quiet -crlf -connect mail.example.com:587
openssl s_client -quiet -crlf -connect mail.example.com:465
openssl s_client -crlf -connect mail.example.com:143 -starttls imap -servername mail.example.com