Check Mail Server Support SSL/TLS To check if a mail server support SSL/TLS, run openssl s_client -connect MAIL_SERVER_IP:PORT -starttls smtp 1 openssl s_client -connect MAIL_SERVER_IP:PORT -starttls smtp Example openssl s_client -connect smtp.elasticemail.com:25 -starttls smtp 1 openssl s_client -connect smtp.elasticemail.com:25 -starttls smtp mail openssl