With 8u121 lower case environment variables worked, but with 8u131 they do not.

Sending lower case environment variables is important because Spring Boot can use them to configure JavaMail, which requires certain lower case properties. For example GMAIL's SMTP server requires spring.mail.properties.mail.smtp.starttls.enable=true. If you convert this to SPRING_MAIL_PROPERTIES_MAIL_SMTP_STARTTLS_ENABLES=true, JavaMail will ignore the value.

I have created a simple project that demonstrates the issue. Build and execution instructions are listed in the README.md. https://github.com/pluttrell/bootvars