Service.EnvConfigProviderSourceRead the configurations from environment variables and set sane defaults.
SMTP_SENDER: Sender address from where the emails come from
SMTP_HOST: Host address of the SMTP server
SMTP_USERNAME: Username for the SMTP server login
SMTP_PASSWORD: Password for the SMTP server login
SMTP_PORT: Port number, default is 587
SMTP_START_TLS: Whether to use TLS, default is true
SMTP_CA_PATH: Location of root CA certificates on the file system
SMTP_CA_CERT: Location of CA certificates bundle on the file system
Either one of SMTP_CA_PATH or SMTP_CA_CERT should be passed or neither of them that triggers use of auto detection. If both are provided, SMTP_CA_PATH will be ignored.