openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 3650To omit the use of a passphrase on the private key, add the following flag
-nodesSMTP
openssl s_client -connect smtp.exmaple.com:25 -starttls smtp
openssl s_client -connect smtp.exmaple.com:587 -starttls smtp
openssl s_client -connect smtp.exmaple.com:465 smtpShow validity range of a cert
echo -n | openssl s_client -showcerts -connect wiki.rlskeels.com:443 | openssl x509 -noout -datesTo test a connection's cert
openssl s_client --connect wiki.rlskeels.com:443