openssl rsa -in asdf.key -out asdf.key

openssl rsa -in asdf.key -text

openssl x509 -in asdf.cert -text

printf "QUIT" | openssl s_client -connect mail.example.org:25 -starttls smtp | openssl x509 -text -noout

printf "\r\n" | openssl s_client -connect example.org:443 2>/dev/null | openssl x509 -dates -noout

openssl req -newkey rsa:4096 -keyout asdf.key -out asdf.csr

(ex. for Thunderbird S/MIME with StartSSL Cert)

openssl pkcs12 -export -out asdf@example.org.pfx -inkey asdf@example.org.key -in 2_asdf@example.org.crt -certfile 1_Intermediate.crt